Yoichi Karasuma has spent all his life training in the mountains. Having accomplished all he can in terms of swordplay up there, he moves onto the next phase of his training. That is to go into the city, the Ikaruga dojo, and learn there. As Yoichi finds out when he reaches the dojo (not before he's arrested), the dojo is run by the four Ikaruga sisters. Yoichi begins attending school in the city and trying his best to fit in while fighters of all sorts begin to arrive either to challenge him or the Ikaruga family.Adapted into an anime for the winter 2009 season.
In addition, Yui Hinagata gets expanded as a villain in the anime, whereas in the manga she, along with her two other friends, were merely giving him the love letter as a joke, and mock him at the end of the chapter. She does make another appearance later in the manga, but she's not a fighter as in the anime, and her competition is with Ibuki rather than Yoichi.
It's largely subverted however, because Ibuki generally gets mad at Yoichi if he seems interested in anyone but her. Even if it was a completely innocent, a Not What It Looks Like situation, or something completely out of his control, such as Angela slipping on a tree branch and landing on him, she tends to beathim up.
Barehanded Blade Block: When this is done to stop a switchblade from shanking him, Yoichi does get his hand cut in the process. Too bad he's too much of a Badass to care, and he proceeds to shatter said switchblade with the same hand.
Big Brother Worship: Sakon towards Ukyou. Touched on a little in the anime, but played straight in the manga. While Sakon developed the potion to make Ibuki have a 4 year old mind in both adaptations, in the manga she did it largely as revenge against Ibuki rather than Ukyou ordering her to as in the anime due to this trope.
Big Damn Heroes: Washizu, Tsubasa, and Angie provide one in episode 12. Particularly cool because the first guy Washizu knocks out was the same one who tased him in the previous episode.
Breakable Weapons: Pretty much any weapon being used near or against Yoichi will be subject to this; one use of his "Nagi" Strike, and whatever it is, be it solid wood or even metal, will be guaranteed to break.
Roku no Tachi: Kogarashi -> Sixth Sword: Fall Wind
Nana no Tachi: Tatsumaki -> Seventh Sword: Hurricane
Hachi no Tachi: Tsumuji -> Eighth Sword: Whilwind
Can't Catch Up: A lot of Ayame's resentment towards Ibuki is the fact that Ibuki seems to be better at her in every way, from academics to athletics, as well as bust size. She largely seems to get over it once Yoichi shows up and tells her that she's special in her own ways and shouldn't be comparing herself to her sister anyway.
The Casanova: Mejiro Tokiya causes all the girls around him to have to be sent to the nurses office. When Ibuki and Ayame don't even give him a second look, he gets upset.
Chekhov's Gun: Kagome's little duck doll. Ibuki helps her to fix it after having it break by accident in an earlier episode. Kagome later uses it to help Ibuki restore her memories.
Clingy Jealous Girl: Ayame sometimes, and especially Ibuki if Yoichi is looking at other girls. Gets expanded in the manga, particularly when Nuezume shows up and threatens to take him away. Ibuki does not take it too well.
Yoichi tears some of Ibuki's clothing in episode 4 in front of her students. She responds by hitting Yoichi and her students.
Tsubasa's Super Mode requires her to be overwhelmed by modesty and shame, and said berserker state is invoked by Angela shredding her clothes, while Tsubasa is talking to Yoichi in a busy school yard.
Later, Tsubasa accidentally rips Angie's dress apart while crying in her room in episode 8. In the manga she does this more often, and Angie at one point notes that she's running out of clothing as a result of Tsubasa's temper tantrums.
Angela manages to cut Yoichi's scarf off in episode 3, but his attack shreds her dress completely.
In the manga, Ayame gets her wardrobe damaged during the play after the lights are knocked out. During the confusion, Ibuki gives her a white sheet, which she ad-libs into the play. Later she wears another dress that the theater club creates for her while dancing with Yoichi, but a bucket of water is thrown on it when she tries to shield Yoichi. Since it was made of toilet paper, the water causes the dress to breakdown.
Color-Coded Characters: In the anime at least. Although none of the women look similar enough to each other that you'd mistake them by appearance alone, they all have different hair colors to help set them apart.
Conservation of Ninjutsu: Blatantly enforced in episode 10, where nearly every single opponent Yoichi has faced (along with a bunch of actualNinja) attack him all at once. Yoichi manages to dispatch all of them in much shorter order than he had when he had faced them earlier.
Corner of Woe: Poor Yoichi and Wa-san both do this often when faced with self-perceived inadequacy.
Nuezume delivers one to Ibuki in the manga, while blindfolded.
Cursed with Awesome: Oboro developed a potion that essentially gives her immortality and eternal youth, but this caused the villagers she lived with to be suspicious of her and turn against her eventually, since they felt she was using them as a guinea pig for her medicine.
Cute Clumsy Girl: Hinted at in the anime, but better stated in the manga. Kagome is given this (additional) explanation as to why she sits out of PE classes.
Delinquent: Ryou Washizu. Though for a delinquent, he's quite the romantic person as far as Ibuki is involved.
Date Peepers: Ayame, Chihaya and Kagome spy on Ibuki and Yoichi during their "practice date".
In the manga, Ibuki herself does this to Yoichi after she thinks he's gotten a love letter asking for a date from Nuezume Aruko, a girl who claims Yoichi as her husband after seeing him use his sword style during the trip to Okinawa. But since Nuezume has No Sense of Direction, she ends up not showing up at all, and Ibuki uses this as an excuse to approach Yoichi.
Also, Washizu lightens up after being stomped by Yoichi twice. To the point where some thugs he previously beat up try to take advantage of it.
In the manga, this gets expanded on, and practically everyone Yoichi defeats ends up helping him in some way later on.
Disproportionate Retribution: Ibuki gets really upset at Yoichi for the simplest things, such as accidentally touching her (or her sister's) breasts, being asked a lot of questions by girls in their class, or even just gawking at another girl.
Evolving Credits: For most of the season, Ukyou and Sakon have their faces hidden by masks until they reveal themselves in-show. The opening follows suit.
The ending of episode 12 is nearly exactly the same as the previous eleven, but for the fact that Ibuki and Yoichi, usually the last character to walk up to the porch and the person sitting on said porch respectively, have swapped places.
Family-Friendly Firearms: While a gun isn't used per se, this trope is in effect. During Washizu's first fight with Yoichi at school, he at first goes barehanded, which Yoichi enjoys (unknown that Washizu really wants to kick his butt). Then he pulls out a weapon. In the manga, he pulls out a switchblade knife, but in the anime, he instead has some cartoonish boxing gloves that resemble a spiked mace. In both versions however, Yoichi stomps him when he sees Washizu relying on weapons like that instead of utilizing his own body.
Possibly Yoichi and his bokken, which he utilizes to defeat anyone who challenges him to a fight.
Fanservice: Repeatedly hits you over the face with it like Ibuki's sword.
First Kiss: Ayame gives one to an unconcious Yoichi during the play. Later, Nuezume gives one to Yoichi after saving him from the ocean. Ibuki is not pleased when she sees that one, particularly when Nuezume claims to be his fiance.
Fish out of Water: Yoichi, who's lived most of his life in the mountains without much human contact other than his father. Although he is quite a skilled swordsman, he has No Social Skills whatsoever, and causes a lot of misunderstandings as a result.
For the Evulz: Oboro, who does various things to the main characters, because she wants to be entertained. Later it turns out that she's doing it as vengeance against humanity because she's Cursed with Awesome and the people around her started turning against her.
Gainaxing: A-plenty in this series, most notably Chihaya on a vibrating massage chair...
Gecko Ending: While the anime didn't diverge too much from the manga (some chapters get combined, such as Sakon giving Ibuki the potion to turn her mind into that of a 4 year old, and she did it on her own, rather than being ordered to do it by her brother Ukyou), it only covers about the first 16 chapters (out of 58).
Gratuitous English: One of the episode previews is delivered completely in English for no apparent reason.
In episode 5, one of the male students in Yoichi's class says "Jesus!" and later "Oh my God!" after Ibuki asks him out on a date.
Green-Eyed Monster: In episode 5, the guys in Yoichi's class who get upset at how much attention Ibuki seems to be paying him, particularly after she asks him out on a Not a Date, to help him "practice" for the real one a girl asked him on earlier.
Practically all the major villains that Yoichi & company face off against in the manga as well. They're usually won over by how strong and determined he is during the fights, and how he gets such power.
Heroic BSOD: Angie suffers one in the manga when she's trying to figure out her feelings for Yoichi. Oboro uses this to her advantage to try and cause Angie to attack him as a result.
Ibuki goes through one after Nuezume beats her in a duel. Ukyou strangely enough, helps her snap out of it.
Yoichi goes through one after hearing that he may be causing trouble for the Ikaruga dojo. It takes Ibuki calling everyone he's helped before to snap him out of it.
Hopeless Suitor: Ayame towards Yoichi. A large part of it is her fault, since she tends to bottle up her feelings for him, and when they do interact, she's often cold and hostile towards him. Then there's her sister Ibuki who tends to beat up Yoichi for so much as looking at another woman.
Also, Ukyo and Washizu towards Ibuki. In their cases, they don't do much to let Ibuki know they're romantically interested in her, so she misinterprets their intentions.
In the later chapters of the manga, Angie falls into this trope as well towards Yoichi. And poor Tsubasa towards Washizu, as he always misinterprets her advances as her being poor (such as when she shows up wearing a bikini, and he thinks she had to sell off her clothes).
I Just Want to Have Friends: Several characters in the manga display this trope, usually villains who are trying to undermine Yoichi's relative success and popularity, such as the student council president and Hinagata during the school festival. Yoichi even calls out the students pretending to like Hinagata on it since they were quick to abandon her when their class was losing out to Ibuki's class in the Maid Cafe contest.
Implausible Fencing Powers: Yoichi frequently displays tenets of this, almost always invoking Katanas Are Just Better (or rather, Wooden Katanas Are Even Better), when he does. The most commonly seen use of this comes in Yoichi's "Nagi" (Lull) Strike, whose purpose is to attack the opponent's weapon with the intent of breaking it. Yoichi's first use of the technique sees him simultaneously fighting twenty-something ninja who, on top of actually being competent and well-trained, were all armed with steel weapons and pumped up on a brainwashing/strength enhancement drug cocktail. Yoichi, who appeared to only be able to block their blows, shatters all of their weapons in short order, using only his trademark bokuto. He later cuts a giant robot to pieces with a tree branch.
Lolicon: On a mental level, anyway. Ukyou attempts to marry (and presumably do other things with) Ibuki while the latter's mind has regressed to a 4-year-old state.
Lost Aesop: Late in the manga series, it is learned that Ibuki, in addition to being crazy strong, was something of a tiny terror, which lead to the Ikaruga parents' departure. This could have been interpreted as a lesson in Responsibility by placing her in charge of the family and the Dojo. In the final volume, we learn that Dad's last opponent Cursed him to involuntarily harm his children, so he simply left to keep his daughters safe from himself.
Love Dodecahedron: To sort this out: Tsubasa likes Washizu. Washizu likes Ibuki, but the feeling is unrequited. Ayame is in love with Yoichi, made complicated by her Tsundere tendencies towards him. Ibuki is definitely in love with Yoichi, as is Angela. With all this attention, Yoichi is still frustratingly dense and unaware of any of this. Chihaya is the only eligible one not involved and seems more interested and amused in the interplay Yoichi causes between her older sisters than with Yoichi himself. Which makes sense since she's a manga-ka.
Recent chapters may already be implying that Chihaya has shown a bit more interest in Yoichi than usual, though.
Love Letter Lunacy: Washizu's unfortunate mixup of Yoichi and Ibuki's lockers in one chapter.
Also Double Subverted when Yoichi receives a completely normal love letter from an unknown girl, which he mistakenly assumes to be a letter of challenge. Ibuki and the other sisters convince him that it's a love letter, but the girl was using the love letter as bait because she actually did want to challenge Yoichi to battle.
Mask Power: Ukyou and Sakon for the first part of the series.
Master of Disguise: Sakon, who at one point disguises herself as Ayame in order to fool Yoichi. She fails only because Yoichi realizes that the "Ayame" in front of him has a larger bust size than the real one does.
Tsubasa is particularly good at this as well, although most of the time we see her skills in action it's largely to put on horror makeup.
Nuezume Aruko from the manga, the daughter of episode 6's villain (who's portrayed a little differently in the manga). She wants to find Yoichi, but often forgets how to find him, and instead of coming to the dojo through the door, she crashes into the window in the bath where he just happens to be bathing at the moment. Later on she, along with her dad, end up all over the place trying to find him again.
Nose Bleed: Yoichi tends to suffer these, either because of a girl or Ibuki beating him up because he's paying attention to another girl.
No Social Skills: Yoichi as a result of living and training in the mountains for nearly all of his life until his father sends him to the city to learn more.
Not a Date: Ibuki denies its one, but asks Yoichi out on one in episode 5. With the intention of teaching him the proper way to go on a date so as to avoid having him do anything stupid. For his part, Yoichi assumes that the practice date is merely that, and doesn't see anything romantic in it. Not that it convinces her sisters however.
Parental Abandonment: While not touched on much in the anime, in the manga, while the Ikaruga sisters were told their parents left for training purposes, they had to leave because their father defeated a man who refused to back down, and consequently cursed him, causing him to nearly kill Ibuki against his will. So they both left in order to keep the sisters safe, although the end of the manga suggests they may be able to lift the curse someday.
Pet the Dog: Washizu gets several moments of this, such as when he fights to protect Ayame from some thugs, and later when he refuses to do anything perverted towards Ibuki while she's temporarily lost her normal mind.
Promotion to Parent: Ibuki is running the place and Chihaya seems to provide for the family by monetary means.
Puppy Love: Between Kagome and Masashi, a mild Tsundere who is a student of Ibuki's dojo and acts as Kagome's protector (oftentimes from her own clumsiness).
Raised by Dudes: Until he comes down from it at the beginning of the story, Yoichi has lived on a mountain his entire life, with only his dad and...
Running Gag: Tsubasa can apparently swap out her form with a teddy bear if she wants to escape Angie. Angie is always amazed at the "body swap".
Sacrificed Basic Skill for Awesome Training: Yoichi in a nutshell. He's an extremely skills swordsman and defeats every opponent who comes along the way, sometimes even without any fighting, but suffers from having No Social Skills and being unable to interact properly with people for quite a while.
Sarashi: Kagome, and Ibuki wears this while training with Yoichi.
Sibling Rivalry: While Ayame greatly respects and looks up to Ibuki, she often feels inadequate when compared to her sister's martial arts skills, bust size, and popularity. The final chapter of the manga ends with the two sisters realizing they're also romantic rivals (for Yoichi) as well.
Stealth Hi/Bye: While Ayame is spying on Yoichi and Ibuki's "practice date" in episode 5, Kagome and Chihaya show up right next to her.
Suicide as Comedy: Yoichi tries to commit sepukku every once in a while, usually when faced with a comparatively minor setback.
Super Drowning Skills: Yoichi is affected by this in the beach episode. Justified as he's lived in the mountains all his life, so he hasn't had a need to learn how to swim. Averted with Kagome, whom the other characters believe suffers from this trope as well, but she's actually quite a skilled swimmer, and dives in to save Yoichi.
Supporting Harem: This seems to be the case. Kagome is too young for Yoichi to be interested in her, Chihaya is probably just teasing him, and Ayame tends to be a Shrinking Violet when it comes to expressing her feelings for him. Tsubasa is interested in Washizu, and while Angela seems to show interest in Yoichi, she never really gets to spend time with him (in the anime anyway. In the manga she gets lots more attention). Then there's the fact that Ibuki gets incredibly jealous if any Yoichi shows any interest in any other woman.
The Power of Friendship: After Yoichi suffers a Heroic BSOD in the manga and leaves the dojo, Ibuki starts calling everyone he helped out earlier, and they all go looking for him, telling him that it was because of him why they're happier and better off.
Fortunately she gets some recognition in the manga, such as when she's performing in the theater club.
Theme Naming: The last names of all the main characters have a bird reference in them. (Karasuma = crow circle, Ikaruga = grosbeak, Washizu = eagle head, Torigaya = valley of birds, Tsubame = swallow, Takatsukasa = hawk government). Tsubasa's first name also means "wing".
Transfer Student Uniforms: Sort of. Yoichi transfers into Ibuki's class at the start of the series, but he never bothers wearing any kind of school uniform, preferring to stick with his samurai clothes.
Tsundere: Ibuki is a type-B, Ayame is a textbook type-A.
Ironic, considering Ibuki is much, much more violently aggressive towards Yoichi than Ayame.
Unprovoked Pervert Payback: According to Ibuki, the correct thing to do when Chihaya jokes that Yoichi should join her and her sisters in the onsen is to beat up Yoichi, on the very flimsy basis that he might have been thinking perverted thoughts. She doesn't even reprimand Chihaya for her joke!
In episode 5, after receiving a letter from a girl, Yoichi innocently asks Ibuki what a date is. She stumbles around for an answer, then gives him a dictionary to look up the meaning since she seems uncomfortable trying to tell him. After he finds out it's a "meeting between lovers", and mentions how cute the girl who gave him the letter is, she gets mad at him and smacks him on the head.
Unrequited Love: Several examples: Washizu towards Ibuki, Ayame (and possibly Angela) towards Yoichi, and Tsubasa towards Washizu.
Unwanted Harem: In this case, the hero is too naive to even know that he even has one.
Vitriolic Best Buds: Washizu and Yoichi are a hybrid of Type I and Type II. Yoichi is openly friendly and unfailingly polite towards Washizu, while Washizu resents Yoichi for beating him and stealing Ibuki's affections, all the while developing a grudging respect and affection towards him. Washizu and Ayame are Type II, connecting over their shared frustrations over their Unrequited Love and encouraging the other to pursue it. When they're not doing this, they spend most their time sparring and insulting each other. Hilariously, their friends mistake this as Belligerent Sexual Tension.
Wise Beyond Their Years: Yoichi, though denser than lead, is able to constantly spout various moralistic/supportive words after any situation he's been thrown into, usually directed at the Villain of the Week. This could just be his idealism talking, but at the same time isn't totally implausible, since he could have studied a wide variety of subjects while up in the mountains.
Wooden Katanas Are Even Better: Yoichi can perform a lot of wind attacks with it (or something similar, such as a long wooden stick), so its justified.
You Fight Like a Cow: Inverted. Yoichi compliments Washizu on the passion behind his punches, even if they are the untrained blows of a delinquent student.
You Gotta Have Blue Hair: Hair Colors in this series go all over the spectrum, with the Ikaruga sisters alone possessing purple (Ibuki), blonde (Ayame), green (Chihaya), and blue (Kagome)-colored locks. Also, hot-pink (Tsubasa) and lilac (Angela).