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-> ''"A choice isn't something someone gives you, it's something you make for yourself."''
-->-- '''Papillon'''

''Buso Renkin'' (literally ''Arms Alchemy'') follows [[TheHero Hero]] and OrdinaryHighSchoolStudent Kazuki Muto, who is killed one night trying to protect a mysterious girl from a monster. However, to his surprise, he [[FirstEpisodeResurrection wakes up the next day]], seemingly good as new. Turns out it wasn't a dream either when the girl, Tokiko Tsumura, shows up again, informing him that she felt responsible for his death and resurrected him with the power of Alchemy. From here on Kazuki discovers his own powers and, together with Tokiko, journeys into the world of Alchemists and their individual [[ImprobableWeaponUser Renkin]] as they fight the monsters known as [[ArtificialHuman Homunculi]]. No, not the ''Manga/FullmetalAlchemist'' kind, though there is definite overlap between the series theme-wise.

A ten-volume manga by Creator/NobuhiroWatsuki, the creator of ''Manga/RurouniKenshin'', it was later adapted into an anime and a light novel. The original manga was serialized from June 2003 to April 2005 in ''Weekly Magazine/ShonenJump'' before being cancelled. Interestingly however, the manga actually managed to have a true ending and somehow actually increased in popularity after completing its run, to the point where it got both said anime and light novel at least a year or two after its completion. The English translation is published under the young adult ''Shonen Jump Advanced'' label.

----
!!Provides examples of:

* TheAce: Shusui Hayasaka is the most impressive student at Ginsei Private Academy. He is the kendo club president who competes at a national level, is the Student Council vice-president, is extremely popular with the girls, is extremely intelligent, and is also more impressive in the trouser department than Kazuki and his friends. Outside of school he is also the best [[spoiler:Familiar of the L.X.E.]]
* AffectionateParody: It's a {{Shonen}} fighting manga by a very well-known author of same that, particularly after the first story arc, starts frequently dipping into screwball comedy and pokes fun at genre conventions like CallingYourAttacks and UnusuallyUninterestingSight.
* AfterSchoolCleaningDuty: At the very begining of the series, SadistTeacher Mita assigns protagonist Kazuki the job of pulling weeds from the courtyard after school as punishment for loosing his school-issue bag. It turns out that the teacher is really the [[OurHomunculiAreDifferent homunculus]] that had [[FirstEpisodeResurrection killed Kazuki the night before]] and only gave him the cleaning duty so he could [[ImAHumanitarian eat him]] somewhere there would be no witnesses.
* AlchemyIsMagic: The series mentions that the RealLife version of alchemy is simply how history records the subject with the more fantastical elements being [[SecretHistory kept from the general public]]. While the transmutation of lead into gold and creation of the the Philosopher's Stone are explicitly mentioned as having failed, the setting's alchemy did lead to the creation of the man-eating and near immortal monsters known as [[OurHomunculiAreDifferent homunculi]] and the kakugane, bulky hexagonal disks that give those that hold one a minor HealingFactor, and can transform into a powerful magical weapon or tool based on the wielder's personality and will to survive.
* AntiVillain: The hawk-homunculus Washio is a NobleDemon who acts as TheDragon for his saviour and creator, the Papillon Masked Creator Koushaku Chouno, during the first arc of the series. While somewhat arrogant, Washio only fights against the protagonists to protect his master and would have let them walk away from their battle if they had sworn to leave Chouno alone. Even after his defeat, Washio still only cares about protecting the Papillon Masked Creator and dies happy after [[StockShonenHero Kazuki]] says that he has no intention of killing Chouno.
* AppendageAssimilation: During their fight at the end of the L.X.E. arc, [[spoiler:the awakened [[BigBad Victor]] and a Victorised Kazuki]] cut off an each other's arms and put them on themselves. Despite the difference in size between the two, the [[AlchemyIsMagic alchemical]] nature of their bodies means that their new arms change to match their physique and skin colour so that it is impossible to tell the difference.
* ArtificialCannibalism: Once a person becomes a homunculus, they get an insatiable lust for human flesh. However the {{Vegetarian Vampire}} Victoria eats her mother's [[BrainFood cloned brain flesh]].
* ArtisticLicenseLinguistics: Dr. Butterfly claims at one point that the words "carnival" and "cannibal" are related. By the author's own admission, they aren't - "carnival" is from the Latin ''carno-'' (flesh) and ''levare'' (put away; "put away flesh", a.k.a. Lent), while "cannibal" is from the Spanish "caribes".
* AstralFinale: When the attempt to forcibly cure [[BigBad Victor]] failed, [[spoiler:Kazuki used the Sunlight Heart Plus' full power to blast the both of them to the moon, so that their WalkingWasteland powers would no longer threaten the Earth]]. With a cure finally complete, the series' {{Denouement}} [[spoiler:has Kazuki's friends and comrades combining their powers to rescue the pair of them]].
* BandageMummy: When [[GenkiGirl Mahiro]] is looking after an injured [[ActionGirl Tokiko]], she overuses the bandages to such an extent that Tokiko ends up totally covered in them, and [[ShoutOut looks like Shishio Makoto]] from the author's previous work ''Manga/RurouniKenshin''.
* BattleCouple: Due to them mostly being involved in individual fights for the majority of the series, the OfficialCouple of Kazuki and Tokiko only fight together a couple of few times, the main times being their defence of the school at the end of the L.X.E. arc, and their brief attack against Victor when they join the final battle that has a more emotional ending.
* BeachEpisode: The summer break trip around halfway through the series has the main characters relax and mess around at the beach[[note]]added due to fan request[[/note]] with surfing, flirting and everyone wearing swimsuits. The episode only serves as a backdrop to set the [[FugitiveArc third arc of the series]] into motion and becomes a WhamEpisode at the end.
* BigGood: Shosei Sakaguchi, the Great Warrior Chief of the Alchemist Army's Asian Branch, is a ReasonableAuthorityFigure who uses his great tactical mind to combat the threat of [[BigBad Victor]]. He is highly respected by the men under his command and is the only one able to keep the resident GeneralRipper in line. During the final battle, Shosei's full plate armour buso renkin, [[HumongousMecha Buster Baron]], when [[PowerCopying combined with those of his subordinates]], is also the only one with enough power to slow Victor down long enough for StockShonenHero Kazuki to arrive.
* BlatantLies: When questioned about their relationship, Tokiko and Kazuki initially try to claim that they are actually siblings, despite the two looking nothing alike and the fact that Kazuki had never mentioned having an older sister to his closest friends. Nobody believed them except his actual [[{{TheDitz}} younger sister]].
* BlessedWithSuck: Becoming a Victor, the third type of being above both human and [[OurHomunculiAreDifferent homunculus]], may bring a person back to life and grant them incredible strength, durability and virtual immortality, but it also makes them a WalkingWasteland that could eventually wipe out all life on earth.
* BrainBleach: Seeing Papillon wearing a mankini on the beach was enough to make [[{{Familiar}} Angel Gozen]] fall apart in shock and cause [[PsychicLink Ouka]] to scream in horror so loud that her nurses became concerned.
--> '''Ouka''': "Somehow, I feel unbelievably frightened..."
* BrainFood: As a non-malicious humanoid homunculus, Victoria satisfies her hunger for human flesh by eating her mother's cloned brains rather than attacking and eating people.
* BrainInAJar: After being paralysed from the neck down, Alexandria, [[spoiler:[[AntiVillain Victor]]'s wife]], transferred her brain life preserving jar to preserve her life long enough to develop a way to [[spoiler:make him human again]]. Over the years Alexandria also repeatedly cloned her brain so that she could link their jars together in an attempt to boost her already genius level intellect.
* BrotherSisterIncest: {{Subverted|Trope}} with the Hayasaka twins who have quite a bit of IncestSubtext when they are first introduced, which is latter explained when their backstory reveals that [[spoiler: they were kidnapped as children and their kidnapper/surrogate mother would have them play game built around wedding vows to build a strong bond between them. When their real parents rejected them, the two legitimately felt like they only had each other, and latched onto the one thing that was happy from their childhood.]] Once they realize that they're not alone, a lot of the creepy subtext gets toned down, and there are hints that Oka may have a crush on Kazuki.
* BroughtDownToNormal: At the end of the series, the Alchemist Army confiscates almost all the kakugane, forcing the Alchemist Warriors to give up the powerful weapons and abilities that they had granted. [[ActionGirlfriend Tokiko]] in particular feels a great sense of loss when hers is taken as she had been fighting with it for almost as long as she could remember.
* ByThePowerOfGrayskull: When someone first learns how to use activate a kakugane, they have to shout out "Buso Renkin!" in order to transform it into their weapon. Once a wielder gains enough experience, [[DownplayedTrope however]], they are able to create their Buso Renkin without saying a word, but most still do anyway.
* CentralTheme: What will you do with the new life given you?
* ClarkKenting: {{Subverted|Trope}} during the attack to the school when Kazuki tries to disguise himself with a scarf covering his face but it doesn't work as his friends have known him so long they can recognize him from afar just by the way he walks and don't even need to see his face. Tokiko's disguise during the same attack is a straighter, if {{Justified|Trope}} example as, while she's just wearing Kazuki's uniform jacket over her usual look, being a very recent transfer student her [[TransferStudentUniforms unusual uniform]] is her most distinguishing feature that can can be seen from a distance, and covering it up does a good job hiding her identity alongside the artificial fog that's blanketing the school.
* ClimacticBattleResurrection: Towards the end of the final arc, Tokiko, Gouta and the Hayasaka twins go to face Papillon [[spoiler:in Kazuki's place]], they find that he has used Alexandria's cloning technology to recreate his [[OurHomunculiAreDifferent animal and plant type homunculi]] minions from the first arc.
* ConspiracyRedemption: While there is [[DownplayedTrope little malice incolved in the decision]], the second half of the series sees the Alchemist Army [[spoiler:attempt to kill [[StockShonenHero Kazuki]] because he will eventually become a WalkingWasteland, and a [[PersonOfMassDestruction tremendous threat to everyone around him]] in six weeks time]]. Things change, however, once the BigBad becomes a more immediate threat -- and the resident BigGood gets the GeneralRipper under control -- and the Alchemist Army lets [[spoiler:Kazuki a spend his remaining time investigating possible cures, and he agrees to allowing himself to be killed if he hadn't found a way to stop or delay the transformation by that time]].
* CreatureHunterOrganisation: While the stated mission of the Alchemist Army is to oversee all aspects of [[AlchemyIsMagic alchemy]] worldwide, and to create the Philosopher’s Stone, the fact that alchemical research has been at a standstill for centuries means that their everyday role is to hunt down and destroy the [[OurHomunculiAreDifferent man-eating homunculi]] created by insane alchemists.
* CreditsRunningSequence: The first scene to show Kazuki in the opening credits of the anime has him running up a hill with Ginsei City in the background, giving a good indication of his straightforward and energetic personality.
* DieOrFly: As a buso renkin is the physical embodiment of the wielder's fighting instinct and will to survive, it is common for people to learn how to summon them when their life is in serious danger. Kazuki, for example, learned how to summon the Sunlight Heart while fighting a homunculus [[note]]Mita in the manga; Saruwatari in the anime[[/note]], while Tokiko gained the Valkyrie Skirt when she was attacked by a captured humanoid homunculus while having her injuries treated with a kakugane.
* TheDitz: Kazuki's younger sister Mahiro is a sweet girl, with GenkiGirl tendencies, who is such a scatterbrain that when her brother and [[ActionGirlFriend Tokiko]] invent the lie that they're siblings immediately believes them and is confused by the fact that nobody told her she had an older sister.
* TheDragon: In the first arc of the series, the hawk-homunculus Washio is the most powerful and trusted creation of Koushaku Chouno, the Papillon Mask Creator. Created from a former {{yakuza}}, Washio is [[UndyingLoyalty totally loyal]] to his creator, and is far more powerful than the arc's BigBad[[note]]until he managed to transform himself into a humanoid homunculus[[/note]], acting as Chouno's bodyguard, enforcer and the ''de facto'' leader of Chouno's homunculi.
* DudeNotFunny: On one occasion in the manga, [[JerkWithaHeartOfGold Gouta]] makes a sarcastic joke about how they'd be able to save on food money if Kazuki stopped eating normal meals and instead just started [[EnergyAbsorption draining]] people whenever he gets hungry. AllLovingHero Kazuki is not amused by the comment and gives Gouta, who he had previously been putting up with, an intense DeathGlare in response.
* EarnYourHappyEnding: Despite the series having a generally light-hearted tone, things get increasingly bad for the heroes, particually [[StockShonenHero Kazuki]], as they are forced to fight against friends, get terribly wounded, have to deal with [[spoiler:turning into a WalkingWasteland]], get separated from loved ones and [[spoiler:exiled to the moon]]. While an [[TakeAThirdOption alternative solutions]] that could help out come along every so often, but something usually happens to delay or invalidate it. The heroes keep pushing on, however, until everything works out in the end, even for the many of the villains.
* EatingTheEyeCandy: During the [[BeachEpisode summer beach trip]], Tokiko wears two-piece swimsuit that exposes her stomach, causing Kazuki to [[LampshadeHanging become mildly obsessed with her belly button]].
* EmpathicHealer: The special ability of the gauntlet part [[StudentCouncilPresident Ouka Hayasaka's]] buso renkin Angel Gozen is to create arrows with a heart motif that, when they hit the target, transfer their wounds to her. She almost died using this ability to prevent [[StockShonenHero Kazuki]] and her brother [[KendoTeamCaptain Shusui]] from killing each other during their fight.
* EmptyPromise: Kazuki's promise to Tokiko that they'd fight Victor together, even if it would kill them both. In the end, he valued her life more than his own.
* EnergyAbsorption: The special ability of the Sword Samurai X, the buso renkin of [[KendoTeamCaptain Shusui Hayasaka]] is to adsorb any energy based attack with its blade and transfer the energy to the cord dangling from its hilt so that the wielder can make a short ranged energy attack of their own. [[Creator/NobuhiroWatsuki The author]] has said that he gave the weapon this ability because he was tired of seeing swords [[SwordBeam firing energy attacks]].
* EngineeredPublicConfession: During the assault on the protagonists' high school at the climax of the L.X.E. arc, one of the students was collaborating with the attacking homunculi and used the intercom to convince the other students that the heroes fighting against the monsters were also enemies so that they students would attack them. When the hero's friends call-out the student over the intercom [[INeverSaidItWasPoison they get him to reveal information that only the attackers would know]], proving that he was working with them.
* EvilLaugh: {{Inverted|Trope}} by Great Warrior Chief Shosei, the BigGood of the series, who indulges in a laugh that would be better suited to a villain, while giving his subordinates a comedic off-screen beating.
* EvolvingWeapon: While all [[EmpathicWeapon buso renkin]] improve and change as their wielder grows in strength and experience, those wielded by warriors becoming a [[WalkingWasteland Victor]] do so to a far greater degree. In the second half of the series, this happens to [[spoiler:Kazuki's Sunlight Heart shrinks in size and weight, internalises its energy and becomes able to produce a size-changing [[LaserBlade energy blade]]]].
* ExpressiveHair: Okakura's large ducktail has a tendency to move and change sizes according to his mood, growing and standing up straight when he annoyed, and drooping when he is depressed. One dream sequence {{Parodie|dTrope}}s this quirk by having his friends manipulate his dream so his hair rolls and unrolls and eventually twist into a drill.
* {{Expy}}: Nobuhiro Watsuki freely admits in the chapter notes that the series protagonist, Kazuki Muto, is a gender-swapped expy of Misao Makimachi from ''Manga/RurouniKenshin''. In addition, he notes (to his apparent surprise) that one of the minor villains is a thinly recast Enishi, and theorizes that he wanted to give Enishi a happier ending through his expy. Many of the other character bios also admit that they are also expies of characters from that series, such as Tokiko being a GenderFlip of Kenshin (or mostly his [[SuperPoweredEvilSide "Hitokiri Battousai" mode]]), Studant Council President Oka Hayasaka is one of EeriePaleSkinnedBrunette Tomoe, and an Alchemist Warrior from later in the series looks like Hiko Seijuro just forgot to shave for a few days.
* ExtraDimensionalShortcut: Silent Trail, the ninja-sword buso renkin of the Alchemist Warrior Shinobu Negoro, can cut open a pathway into another dimension that only its creator can enter so that they can disappear and then reappear elsewhere to make a sneak attack on an opponent.
* EyepatchOfPower: The [[OurHomunculiAreDifferent homunculus]] Washio has multiple blond bangs covering his left eye, giving him a predatory look that fits with his hawk AnimalMotif.
* EyePoke: Tokiko has a noted preference for attacking peoples in the eyes when annoyed, such as during the epilogue when she catches Kazuki staring at her scar and performs an eye poke as punishment.
--> '''Watsuki:''' Tokiko loves to go for the eyes. Kazuki loves to bleed.
* EyeScream: During her fight with the rose homunculus Hanabusa during the A New Life arc, Tokiko jams her fingers into her opponent's eyes and rips them out before beheading her with the Valkyrie Skirt.
* TheFaceless:
** After [[StockShonenHero Kazuki]] sees Captain Bravo for the first time in his face-concealing trenchcoat, [[ActionGirlfriend Tokiko]] says that she has never seen his face, despite working under his command for a while. This is {{Subverted|Trope}} later, however, as when the pair get back to their dorm, they find that they new Dorm Manager acts and speaks exactly like Captain Bravo, and they immediately work out who he is.
** For the majority of the series, Alchemist Warrior Busujima is never seen without her gas mask buso renkin, only revealing her cute face briefly in the epilogue. While the Japanese audio for the anime also distorts her voice [[AmbiguousGender so that it is impossible to tell her gender]], the English dub uses a more obviously feminine voice.
* FallingIntoHisArms: {{Subverted|Trope}} during the first arc when Kazuki tries to catch Tokiko, who had been launched into the air by his energy-propelled Sunlight Heart, only for him to almost be impaled by the lance as Tokiko uses her [[SpiderLimbs Valkyrie Skirt]] to safely land behind.
* FanDisservice: [[AntiVillain Papillon's]] outfits, ranging from his regular ice dancer-inspired bodysuit to his butterfly embroidered speedos, would be quite attractive on a more traditionally attractive man but become disturbing on someone with his somewhat gangly limbs and pasty skin, especially the frequent crotch shots. It's PlayedForLaughs on multiple occasions, including a BeachEpisode in which he wears a mankini that makes his ally scream in horror.
* FeatheredFiend: Washio, the eagle homunculus, is the strongest of the man-eating animal-type homunculi who is able to transform into a half-man/half-bird hybrid [[TheHeavy who gives the main characters their toughest fight]] of the A New Life arc. By the end of the arc, [[SubvertedTrope however]], it is revealed that Washio is actually a NobleDemon who doesn't care about anything except protecting the master who brought him back to life.
* FiveSecondForeshadowing: As Papillon picks up Doctor Butterfly's kakugane, the audiance can see that it has [[spoiler:the same ''unique'' serial number as Kazuki's]]. Moments later [[spoiler:the shell on Kazuki's kakugane breaks away to reveal that it is actually a black kakugane, the same type that created the BigBad Victor]].
* FoeRomanceSubtext: Papillon's obsession with Kazuki [[DefeatMeansFriendship after his defeat]] involves a one-sided romantic subtext. This is magnified by how there's already a lot of subtext around Papillon with his distinctive and flamboyant outfits, mannerisms and butterfly mask.
* FromTheLatinIntroDucere: Doctor Butterfly once claims that the words "carnival" and "cannibalism" are related. They aren't ("carnival" actually derives to abstention from meat for Lent). Watsuki acknowledges the mistake in the author's notes of the manga and suggests the reader consider it Butterfly's screw-up.
* FugitiveArc: After Kazuki discovers that he has a [[spoiler: black Kakugane and is turning into a WalkingWasteland]], the third arc of the series sees him, Tokiko, and Gota are hunted by their former allies from the Alchemist Army.
* FullFrontalAssault: Alchemist Warrior [[BloodKnight Genji Ikusabe's]] Buso Renkin, Gekisen gives him a HealingFactor that can quickly regenerate his body FromASingleCell but doesn't restore his cloths. As a result of this, after being blown to pieces early on Ikusabe spends the rest of his fight against Papillon totally naked as he is enjoying himself too much to care.
* GenkiGirl: While it is {{Downplayed|Trope}}, particularly in the second half of the series, Mahiro Muto is noted in-universe as being a female version of her StockShonenHero big brother Kazuki, being a hyperactive [[TheDitz scatterbrain]] who repeatedly [[TheGlomp glomps]] her brother's [[ActionGirlfriend love interest Tokiko]].
* GentleGiant: Masashi Daihama is a large and upbeat but soft-spoken boy, who [[ApologeticAttacker dislikes violence]] and is the most normal of [[IdiotHero Kazuki's]] school friends. [[BewareTheNiceOnes When he is forced to use violence]], however, he is able to break open a locked door with ease.
* GivingUpTheGhost: Kazuki's soul will often attempt to leave his body when Tokiko hits him during the more lighthearted moments of the series, such as after his [[EpicFail disastrous]] attempt to emulate the seductive 'Bravo Kiss' during the BeachEpisode.
* GoryDiscretionShot:
** At one point in the series a [[OurHomunculiAreDifferent homunculus]], already in pain from wounds inflicted by Tokiko, pleads for her to stop. Tokiko responds by plunging her blades into him. Jump cut to shot of the sky, and a moment later, scream of agony.
** In the manga, when Tokiko [[EyeScream yanks out Hanabusa's eyes]] her body and a dialog bubble block the reader's view of the act.
* GratuitousEnglish: The names that Kazuki initially came up with [[CallingYourAttacks for his attacks]] are in English, usually following the theme of "Jousting Something". When Tokiko named Kazuki's kakugane, she also kept it in English, calling it the Sunlight Heart and Kazuki changed the names to "Sunlight Something".
* GreenEyedMonster: Koushaku Chouno's younger brother Jirou deeply resented being born as nothing but a backup heir. Even when his brother was declared unfit and the title of heir was passed to him he still resented that he only got what he wanted because of Koushaku's ailing health rather than merit. When his brother was trying to save his life, and told Jirou that even if he got better he didn't care about the family and wouldn't take back the title of heir it wasn't enough, leading to Jirou trying to destroy the one thing that would save his twin's life.
* HadesShaded: Those becoming a [[WalkingWasteland Victor]] are able to take on a heavily tanned or bronzed form that becomes permanent once they reach Stage 2 of their transformation. Once a Victor reaches Stage 3, as [[BigBad Victor]] himself did towards the end of the series, their skin-tone darkens even more, becoming blackened as if burned or in permanent shadow.
* HealingFactor:
** Gekisen, the cross-spear buso renkin of Alchemist Warrior Genji Ikusabe, gives him the ability to regenerate any wound inflicted on him, up to and including the [[FromASingleCell complete destruction of his body]], as long as he was holding the spear when the wound was inflicted.
** All [[OurHomunculiAreDifferent homunculi]] have a natural healing factor that allows them to almost instantly regenerate any damage caused by non-alchemical means. A homunculus can also regenerate damage cause [[AlchemyIsMagic alchemy]] but it takes longer and if their emblem mark weak point is destroyed then they will die.
* HealingVat: Dr. Butterfly spent the hundred years prior to the tart of the series developing a large restoration tank that would allow him to heal the seriously wounded [[BigBad Victor]] through the power of [[AlchemyIsMagic alchemy]] and tested it by bringing his great-grandson [[AntiVillain Papillon]] back to life after his destruction. After Dr. Butterfly's defeat, Papillon inherits the designs, often using them to heal and revitalise himself.
* HiddenDepths: While she has the outward character of a YamatoNadeshiko, the fact that the personality for Oka Hayasaka's hyperactive and sarcastic buso renkin {{familiar}} Angel Gozen is based on her subconscious mind shows that she is a more complex character than she lets on.
* HighTechHexagons: Hexagons are a recurring motif for almost anything involving alchemy in the series. Despite being [[AlchemyIsMagic magical]], most alchemical devices have a high-tech mechanical design, the most prominent being the kakugane, a four-inch wide hexagonal device that transform into the {{Magitek}} weapons.
* HorrorHunger: All homunculi are driven to consume human beings even though they can survive without doing so as the end of the series [[spoiler:saw them exiled to the moon where they seemed to be able to survive without a food source]]. It has been theorised, in-universe, that this hunger for human flesh is the result of a deep desire to become human once again.
* HumongousMecha: Great Warrior Chief Shousei's full plate armour buso renkin Buster Baron takes the form of a 57-meter tall robot knight. As well as its immense strength, Buster Baron has the ability to [[PowerCopying copy the buso renkin]] of anyone in its sub-cockpits, enhancing the powers of the weapon in proportion to its size.
* IllBeInMyBunk: During the Buso Renkin Seminar omake at the end of the anime's 5th episode, Mahiro begins talking about what she wants to do with Tokiko if she becomes her big sister via marrying Kazuki, getting increasingly excited before realising that she is letting her imagination run away with itself and says she will continue when she gets back to her dorm later on.
* ImmortalityImmorality: Becoming a near immortal homunculus generally requires human experimentation that can result in the deaths and forced transformation of many humans. In addition to this, once an individual becomes a homunculus, they suffer from a psychological HorrorHunger that compels them to consume humans [[spoiler:even though this isn’t an actual necessity]].
* ImprobableHairstyle: Hideyuki Okakura, the most hyperactive and loud of [[StockShonenHero Kazuki's]] friends, has a ridiculously large pompadour that would be impossible in real life without some internal support.
* IncredibleShrinkingMan: In the manga version of the series, both [[BigBad Victor]] and [[ActionGirl Tokiko]] are shrunk after getting hit Madoka Maruyama's Bubble Cage buso renkin[[note]]the anime changed Bubble Cage's power to simply creating explosions[[/note]]. While Victor isn't shrunk by much, Tokiko was reduced to the size of a doll until she defeated Maruyama.
* IronicEchoCut: In their attempt to infiltrate Ginsei Academy, Tai and Shi, a pair of large [[OurHomunculiAreDifferent homunculi]] with limited intelligence, talk about how perfect their disguises are before the scene cut to the students saying how suspicious the two massive guys wearing badly fitting school uniforms are.
-->'''Tai and Shi''': "''Our disguises are perfect! We do not look suspicious!''"
-->'''Every student who sees them''': ''"Those two look suspicious!''"
* KendoTeamCaptain: TheAce Shusui Hayasaka is the captain of the Ginsei Private Academy Kendo Club, the Student Council Vice-President[[note]]under his twin sister Ouka[[/note]] and the most popular male student in school. When first introduced he becomes a friendly rival for StockShonenHero Kazuki as he is the only person willing to train with the exceptionally skilled Shusui before it is revealed [[spoiler:that he is working for the man-eating monsters of the L.X.E]].
%%* LaughablyEvil: Papillon. What other villains do you know who will fight you wearing just a butterfly mask and Speedos?
%%** Also, Moonface.
* LiteralChangeOfHeart: Both Kazuki and [[spoiler:Victor]] have their hearts replaced with an [[{{Magitek}} alchemical device]] known as a kakugane after their own were damaged beyond repair, allowing Kazuki to become a StockShonenHero while [[spoiler:triggering Victor's StartOfDarkness when the [[WalkingWasteland unknown side-effects]] became apparent]].
* MaskedVillainsUnmaskedHeroes: The StarterVillain Papillon wears a butterfly mask, while the hero Kazuki wears no face coverings. Papillon later becomes an AntiVillain.
* MeaningfulAppearance: The ninja Alchemist Warrior Shinobu Negoro has a large, triangular bang covering his left eye that symbolises his fighting style that relies on concealment, dirty tricks and his ExtraDimensionalShortcut powers.
* MistakenForDestitute: Downplayed. Kazuki is surprised to find Tokiko living in a nice hotel. She asks him if he imagined that she lived in the clouds sipping mist. He shows an ImagineSpot of her living in a cardboard box huddled under an old blanket. Tokiko, less than amused about that, shouts, "You're damned rude!"
* MyGreatestFailure: Both Mamoru Sakimori and Sekima Hiwatari were utterly devastated by their team's failure to stop the school massacre that left [[TheLancer Tokiko]] as its SoleSurvivor. The effect of this failure was so profound that both assumed new personas following the tragedy to deal with their grief: Sakimori becoming the LargeHam Captain Bravo, while Hiwatari becoming a ColonelKilgore and GeneralRipper.
* MySuitIsAlsoSuper: Shinobu Negoro's Silent Trail buso renkin should only allow his body to pass through the ExtraDimensionalShortcut it creates, yet he is able to move through it fully clothed. During his fight with the {{Ninja}}, however, Gouta [[AwesomenessByAnalysis works out]] that Shinobu's cloathes have been laced with his hair to allow them to pass through as well.
* TheNeedless: Individuals undergoing Victorization no longer need any food or oxygen as their bodies are sustained by their ability to absorb LifeEnergy from the surrounding area. Even when removed from a source of life energy, such as [[spoiler:on the Moon]], Victor-type beings can survive without sustince for time, mearlly becoming exausted.
* NighInvulnerability: Anyone who reaches the later stages of Victorization, such as the BigBad Victor himself, become all but impervious to any regular or [[AlchemyIsMagic alchemical]] attack, and even when an extremely powerful attacks does manage to do some damage, it is quickly repaired by their HealingFactor. Only wounds caused by another Victorized being have any chance of doing serious harm.
* NobleDemon: The hawk homunculus Washio is a man-eating monster but his UndyingLoyalty, his desire to repay his master for bringing him BackFromTheDead, and the honour he shows during his fight with Kazuki and Tokiko gives him a morale grounding that Chouno's other animal-type homunculi lack.
* NoIAmBehindYou: In the manga version of Kazuki's fight with Shusui, the two of them chain a long string of flashes behind each other's backs until they are [[ParodiedTrope at the other side of the school entirely when they stop]]. The in-universe explanation for this is that Kazuki did it on purpose so that the fighting wouldn't destroy the school, and Shusui was humouring him but the mangaka admitted that he did it because he was having trouble plotting out a 2-on-2 duel, so he came up with an amusing way to separate the fighters to make two simultaneous, but separate, 1-on-1 duels.
* OfficialCouple: Kazuki and Tokiko were effectively a couple by the end of the first arc and were together for the rest of the series. Even Gouta, the only other character with romantic intentions towards Tokiko, accepted that the pair belonged together by the end of the series.
* OhCrap:
** Tokiko shows a panicked and shocked expression when, after failing to destroy the parasitic homunculus core dangling from Mahiro's hair, it to come towards her instead, and she has no way to block it.
** Despite his [[BloodKnight love of battle]], Warriors Chief Hiwatari's face shows that he is shocked and dismayed when he sees Victor without a scratch after taking a full-power attack of Sakaguchi's HumongousMecha buso benkin.
* OneSuperOnePowerset: Justified. If a kakugane wielder uses a different kakugane they just get the same buso renkin with different styling. Likewise homunculi can't gain new abilities, though as evidenced by Washio they're perfectly capable of training to use their existing powers more effectively. [[spoiler:Subverted by Victors, which appear to get a new buso renkin from their kakugane being turned black.]]
* OurHomunculiAreDifferent: Homunculi are the result of [[AlchemyIsMagic alchemical research]] into immortality. There are two broad types of homunculi in the series, non-humaniod homunculi made from a combination of human and non-human material (animal or plant) that can switch between a human form and a hybrid form that has powers related to their non-human material, and humanoid homunculi who retain their human mind and appearance. Both types of have an insatiable desire for [[ImAHumanitarian human flesh]] and can only be killed by the power of alchemy (such as the weapons known as buso renkin or other homunculi damaging the sigil on their bodies.
* PartialTransformation: The [[OurHomunculiAreDifferent hawk-homunculus]] Washio is unique amongst that animal-type homunculi as he is able to only partially transform into his bio-mechanical animal form, changing his arms and hands so that he can use his razor-sharp claws and shoulder-mounted wings. This hybrid form allows Washio to make greater use of his strength and speed, while still allowing him to read the wind with his metallic feathers in order to predict his opponent's moves.
* PlantPerson: Hanabusa is a [[OurHomunculiAreDifferent rose homunculus]] whose monstrous form is that of a massive, part-mechanical rose with a vine wrapped human torso emerging from the stem. She fights using thorn-covered vines as CombatTentacles.
* PoisonAndCureGambit: After one of his Homunculus embryo [[EvilGenius the Papillon Mask Creator]] attaches itself to [[ActionGirlfriend Tokiko]], he offers [[StockShonenHero Kazuki]] a cure in exchange for Kazuki's [[MacGuffin Kakugane]], a rare [[AlchemyIsMagic alchemical device]] that can turn into a powerful weapon and posssesses healing properties. This is also an unintentional XanatosGambit, given that the cure [[spoiler:is a useless fake]] - if Kazuki makes the trade, then Papillon gets to study Kakugane technology and he ''still'' gets to turn one of his greatest enemies (at the time) into a minion. If not, then he loses out on the Kakugane but still gets Tokiko as a minion. However, because the Kakugane is what brought Kazuki BackFromTheDead, he can't remove it or he'll die [[spoiler:so he doesn't make the trade and accidentally knocks out the Papillon Mask Creator with one punch, at which point Tokiko arrives and tells him that the cure was fake.]]
* PornStash: During the first arc of the series, when [[StockShonenHero Kazuki]] talks to his friends on the phone to hear their voices and gain strength from their friendship, Koji Rokumasu, the most level-headed and intelligent of his friends, [[ImpliedTrope mentions]] that he had hidden Kazuki's dirty magazines so that [[ActionGirlfriend Tokiko]] wouldn't find them.
* PostFinalBoss: The last battle of the series takes place after the BigBad has been defeated, [[spoiler:and Kazuki cured of his Victorization, is Kazuki's rematch with Papillon]] to finally resolve their rivalry from the end of the first arc.
* PowerFist: Peaky Gulliver, the buso renkin of the humanoid homunculus Kinjo, takes the form of an armoured gauntlet. The gauntlet is able to boost Kinjo's attack power, as well as spin [[ThisIsADrill around like a drill]], has rocket boosters that can [[RocketPoweredWeapon propel his attacks]] and [[{{Sizeshifter}} grow to a massive size]].
* PowerDyesYourHair: When a person transforms into one of the super-human {{Walking Wasteland}}s known as a Victor their hair turns white (light green in the anime) and gives off an [[PowerGlows eerie glow]].
* RedOniBlueOni: Kazuki is the Red Oni, being highly excitable StockShonenHero, who prefers direct UnskilledButStrong attacks and is passionate about saving people. His [[BattleCouple love interest]] Tokiko meanwhile is a somewhat calmer Blue Oni character who is totally dedicated to her mission and is not above using underhanded tactics in battle alongside her WeakButSkilled fighting style. The main colour palates for the two are also red/orange and blue respectively. These aspects are {{Downplayed|Trope}}, however, as when not fighting Tokiko can be as loud and violent as a Red Oni when she has to deal with the idiocy of Kazuki and his friends.
* RedundantRescue: Kazuki was [[CallToAdventure pulled into the story]] when he attempts to [[TheDulcineaEffect save a girl from a monster in an abandoned factory]] only to end up dead. Tokiko, the girl in question, is able to [[FirstEpisodeResurrection revive Kazuki]] and later explains that she is an Alchemist Warrior who was luring the monster out of hiding so she could kill it - [[SenselessSacrifice meaning that Kazuki died for nothing.]]
* ReptilesAreAbhorrent: Kawazui, a [[OurHomunculiAreDifferent Surinam Toad homunculus]], is the most villainous of the animal-type homunculi from the series' first arc. While most of the homunculi are either driven by their hunger or a deep dedication to their creator, Kawazui has a slimy, greedy and torturous personality, while his role as a spy gives a very stalkerish feel to his character.
* RescueIntroduction: Kazuki first met Tokiko when he tried to save her from a man-eating homunculus. The rescue didn't go to plan, however, as Kazuki suffered a mortal wound, forcing Tokiko (who was only pretending to be in danger to lure the homunculus into a trap) to [[FirstEpisodeResurrection bring him back to life]] with a {{Magitech}} kakugane, making it a mutual rescue introduction
* RobotDog: Killer Rabies, the buso renkin of Alchemist Warrior Rintaro Inukai, takes the form of a pair of Alsatian-sized robotic dogs that he commands with a whistle. Rintaro uses his dogs as {{Attack Animal}}s in battle and can make them go berserk so that they will attack anyone not holding the command whistle.
* SayItWithHearts: Papillon [[InsistentTerminology insists]] that everyone uses hearts when saying his name to the point that it is almost his CatchPhrase.
-->'''Tokiko:''' Papillon!\\
'''Papillon:''' ''[while wagging his finger admonishingly]'' Papillon♥. You have to say it with love!
* ScaledUp: The monstrous form of Mita, the first [[OurHomunculiAreDifferent animal-type homunculus]] that Kazuki faces in the series, is that of a mechanical king cobra [[SpikesOfVillainy covered in spikes]] and large enough to [[SwallowedWhole swallow a person whole]].
* SealedEvilInADuel: The final battle between Kazuki and the BigBad results in using the full power of his weapon to [[spoiler: launch himself and Victor to the moon]] where they can fight without harming anyone until [[spoiler:a cure for their WalkingWasteland condition can be created]].
* SecretHistory: When first introduced to alchemy at the beginning of the series, [[StockShonenHero Kazuki]] looks it up in an encyclopedia, discovering a description similar to that of the real world mentioning that its main goals were the PhilosophersStone and transmutation of base metals into gold. [[ActionGirlfriend Tokiko]] explains that this is only what the public know about the subject as the [[OurHomunculiAreDifferent homunculi]] and the {{magitek}} weapons known as buso renkin were kept secret.
* ShapeshiftingExcludesClothing: During her manga-only fight against Madoka Maruyama, [[ActionGirl Tokiko]] gets [[IncredibleShrinkingMan shrunk to eight inches tall]], leaving behind the clothes she was wearing in a pile on the floor and forcing her to improvise some new clothing out of bandages until she can find some doll-sized clothes.
* SharedFamilyQuirks:
** As well as their intelligence and alchemical skill, both Papillon and his great-grandfather Dr Butterfly share the same flamboyant fashion sense and an obsession with butterflies.
** A number of characters at the begining of the series note that Mahiro is essentially a female version of her older brother Kazuki, with the same hyperactive personality and taste in food. It is even implied that Mahiro shares an interest in Kazuki's love interest Tokiko.
* ShooOutTheClowns: Following the LXE arc, the series gets a little more serious as [[BigBad Victor]] is awake, [[spoiler:Kazuki will become like him in six weeks, [[FugitiveArc and a team of Alchemist Warriors is sent out to kill him before it happens]]]] and from this point on Kazuki's primarily ComicRelief school friends and sister are left behind, only having cameos or the rest of the series.
* ShoutOut:
** Shusui Hayasaka's buso renkin, Sword Samurai X, is a shout-out to ''Manga/RurouniKenshin'''s original English title, ''Samurai X'' that Creator/NobuhiroWatsuki said he really liked. There is also, a shout-out to the same series for a single panel in the manga where Tokiko is so bandaged up, she looks like Makoto Shishio, for no reason other than an irresistible impulse the author had.
** The Alchemist Army's training room being called the Danger Room and the {{Big Bad}}'s weapon being named Fatal Attraction are shout-outs to ''ComicBook/XMen'', Watsuki's favourite American comic series.
** In one episode, the camera makes a panning shot of a TV and onscreen is the main character from Nobuhiro Watsuki's one-shot, "Embalming -Dead Body and Bride-", that would later be worked into his subsequent series ''Manga/{{Embalming}} – The Another Frankenstein Tale''.
** When Kazuki draws up a composite sketch of Papillon, the art style is that of ''Manga/JojosBizarreAdventure'' creator Creator/HirohikoAraki.
* SomberBackstoryRevelation: In the final chapter, Kazuki asks Tokiko if he can touch her [[GoodScarsEvilScars signature scar]]. Embarrassed, she runs off. When they finally meet up, she explains her past to him. Her school was slaughtered by a homonculous, and she was the SoleSurvivor, but with no memory of her past. She was taken in by the Alchemist Warriors, and a Kakugane [[AppliedPhlebotinum was placed on her to heal her injuries]]. The self-same homonculous showed up, trying to take it from her, slashing her face in the attempt. In that moment, her will to fight awakening, she manifested her Valkyrie Skirt for the first time, slaughtering the homonculous before the rest of the Alchemist Warriors arrived. She feels the scar marks her birth as a warrior. After relating the story to him, [[IfItsYouItsOkay she gives Kazuki permission to touch her scar. ]]
* SpamAttack: The offensive ability of Ouka Hayasaka's Angel Gozen buso renkin is to use its floating automaton to quickly generate and fire a massive amount of energy arrows at the target in an attempt to overwhelm their defences with sheer volume of fire.
* SpoilerOpening: Those watching closely will see that the anime's opening reveals that [[spoiler:Kazuki's kakugane is really the dangerous Black Kakugane III, not Kakugane LXX as was previously thought.]]
* StockFootage: As he is a minor character with few scenes, the same animated sequence showing the Alchemist Warrior Ikusabe [[FromASingleCell recomposing his entire body]] is used three times during his fight with Papillon.
* SwordBeam: [[InvertedTrope Rather than shooting energy beams]], the katana buso renkin "Sword Samurai X" has the ability to [[EnergyAbsorption absorb and nullify enemy energy attacks]]. The writer, Creator/NobuhiroWatsuki, dislikes swords that fire energy attacks, believing that they defeated the very purpose of a sword, so he gave the weapon the ability to nullify such attacks instead.
* TakeAThirdOption: Kazuki, the main character, has a habit of trying to choose a third option, even [[LampshadeHanging actually calling them out loud while doing so]]. The best example of this is towards the end of the series when Kazuki is faced with the choice to either use the white kakugane on himself and save his own life, or use the white kakugane on Victor and save the world. With Papillon's help he comes up with a third option of simply making another white kakugane and saving them both, but [[spoiler: the white kakugane doesn't work entirely on Victor]]. So obviously he comes up with the fourth option of [[spoiler: sending them both to the moon and supposedly killing both of them]].
* TalkingIsAFreeAction: During a kendo sparring session between [[StockShonenHero Kazuki]] and [[KendoTeamCaptain Shusui]], four people comment on Shusui's reverse-dou strike between the time he starts swinging and the time it connects. This then {{Lampshade|Hanging}}d when one of Kazuki's fainds says that it is taking too long.
* TeleportationWithDrawbacks: One of the abilities of Chitose Tateyama's radar buso renkin, the Hermes Drive, is to teleport the user, and other objects up to a total weight of 100 kilograms. As the range and number of times it can be used depends on Chitose's willpower and stamina, this ability is usually only used for emergency situations such as gathering a team quickly or to evacuate people from combat.
* ThatWasNotADream: After their first encounters with homunculi, both Kazuki and Mahiro both believe what they experienced was AllJustADream until they are attacked a second time. Neither of them reacted too drastically to the revelation, however, with Mahiro even taking comfort from it as it meant that Kazuki had saved her and would do so again.
* ThisIsGonnaSuck: In the first arc, when [[StockShonenHero Kazuki]] tackles [[ActionGirlfriend Tokiko]] to prevent a Homunculus core bonding with her, the pair tumble down a hill and he hits his head constantly against rocks on the way down. When he sees the last rock (a fairly big one), he comments that it is going to hurt but takes it anyway, hugging Tokiko closer to him, despite the fact that he knocked himself out.
* {{Tuckerization}}: The author, Creator/NobuhiroWatsuki, named the series' main character, Kazuki Muto after Creator/KazukiTakahashi, with his surname coming from Yugi Muto, the main character of Takahashi's most famous work, ''Manga/YuGiOh''.
* TwoScenesOneDialogue: The beginning of the L.X.E. arc sees the exposition on the BigBad done as two simultaneous conversations: The main protagonists are informed on the subject by [[TheGoodCaptain Captain Bravo]], while [[TheDragon Dr. Butterfly]] does the same for AntiVillain Papillon.
* TheUnfavourite: Due to his poor health, Koushaku (a.k.a. [[AntiVillain Papillon]] became the un-favourite to similar-looking younger brother Jirou, who had previously believed himself to be the un-favourite due to his elder brother's intelligance and preferential treatment. Part of the reason Koushaku is AffablyEvil towards Kazuki seems to be that Kazuki was the first person to ever really care about him, even if it was in an ArchEnemy sort of way. Owing to that, Kazuki is the only one Koushaku allows to refer to him by name rather than by his Papillon alias.
* UngratefulBastard: After learning about Shusui and Ouka's tragic past, Tokiko doesn't feel sympathy for them, claiming that wanting to becoming man-eating homunculi and making other people suffer is unforgivable as she goes to attack them. Kazuki, however, refuses to let Tokiko kill them and puts his life at risk to defend them from her, only for Shusui to use the opportunity to stab Kazuki through the abdomen. Luckily, Ouka is grateful for Kazuki's actions and [[EmpathicHealing saves his life]].
* WalkingWasteland: Draining LifeEnergy is an inherent ability of all Victor-type beings comparable to breathing for a normal human so they will eventually kill everything around them whether they want to or not. The strength and area effected by this Energy Drain effect increases as the Victorization progresses, so if Kazuki hadn't [[spoiler:taken Victor to the moon until a cure could be found]] all life on earth would have eventually been destroyed.
* WhamEpisode: Chapter 49 of the manga and Episode 16 of the anime sees things change drastically for the main characters as [[spoiler:Kazuki is revealed to only have six weeks of humanity left as he is turning into a monstrous WalkingWasteland, and his allies in the Alchemist Army turns on him to prevent him from becoming just like the BigBad.]]
* WhatIsEvil: Papillon questions whether he or Tokiko is the evil one when he only killed in an attempt to prolong his own life while she kills a humonculus after telling it that it would feel the pain of hell before it dies.
--> "Oh my, it begs the question, which of us is the truly evil one"
* WhatTheHellHero: Victor calls out Great Warrior Chief Sakaguchi for repeating the mistakes of the past for [[spoiler:ordering the Kazuki's termination after he begins the Victorization process]] as this happening to him was what originally caused Victor himself to begin his quest to wipe out alchemy and anyone who uses.
* WhenTheClockStrikesTwelve: During the first arc of the series, [[ActionGirl Tokiko]] is infected with an alchemical parasite that will turn her into an [[OurHomunculiAreDifferent homunculus]] once it reaches her brain a few days later. When they eventually confront the creator of the parasite, he claims that the transformation will happen at midnight, although why it would happen exactly at that time is never stated.
* WhipOfDominance: Noisy Hamelin, the buso renkin of the humanoid homunculus Jinnai, take the form of a whip that uses sound waves to [[MindControlDevice control all humans in the area]]. The design of the whip is based on those used by circus lion tamers and to fit with Jinnai's pet breeding hobby.
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