AIKI is a {{Seinen}} action manga, written and drawn by Isutoshi, an [[BleachedUnderpants artist mostly known for doing H-manga]]. However, as the series has progressed, the manga has tilted more towards martial arts and comedy and less towards the ecchi side (though a good amount of FanService still remains).

The story features Kunitoshi Joukyuu, a young martial artist who is so strong that his father/teacher actually dislocated (and then relocated) all of his joints within one night just so he would only be able to access half of his power, in an attempt to teach him either humility or creativity. Even so, he constantly wipes the floor with the competition, to the point where a couple of muscular female teachers beg him to train their [[TheOjou "mistress"]]: a small, raven-haired girl named Kizuki . While Kizuki knows a decent amount of Aikido on her own, she's the granddaughter of the chairman of the school board and a high-value target because of the school's politics.

Of course, it doesn't help that most of Juzenji High School is out to defeat Kizuki, or that Kunitoshi's scantily-clad, female cousin Miu Takatori(who's the principal's daughter and Kizuki's main opponent for control of the school) is trying to recruit him [[KissingCousins by any means necessary]]. Not to mention that Kunitoshi himself is a JerkAss [[LovableSexManiac pervert]] who constantly arranges for his students to be [[FigureItOutYourself thrown into dangerous situations]] and may be the [[AntiHero worst role model ever]]. Despite all this, Kunitoshi grudgingly trains a growing group of women into skilled martial artists while battling a SortingAlgorithmOfEvil as he looks for a way to regain his previous strength.

In short, think of AIKI as a much more lewd and evil version of ''KenichiTheMightiestDisciple''.

Gained a sequel called Aiki S which is currently in publication.

!!This series features examples of:

* AbsoluteCleavage: In pretty much every chapter.
* ActionGirl: Any girl with a name in the story, and even some without them.
* AmazonianBeauty: Houmei is extremely muscular at the start of the manga, such that it actually slows her down in fights and she has to slim down a little bit to be effective. Kageyasu's no slouch in this department either, with a nice set of washboard abs and biceps.
* ArrogantKungFuGuy: Kunitoshi
* AuthorTract: The sheer weary one-sided contempt and amoral cynicism pouring out of Isutoshi these days is pretty staggering. Before that ''[=TendeFreeze=]'' and even ''Slut Girl'' were comparatively lighthearted and optimistic, with the only real author tracts being the FanService, the uncommonly beautiful female designs, [[DeadpanSnarker some tongue-in-cheek sarcasm]], and strong influence from assorted 1990s fighting video games.
* AwesomenessByAnalysis
* BadassGrandpa: Kaneoto Houju. Due to old age, he has only about a tenth of Kunitoshi's speed and lacks the stamina to fight for more than 30 seconds, as well as rheumatism and cataracts. He still manages to fight Kunitoshi to a draw. Arguably the most skilled character to appear in the original manga.
* BattleHarem: It features only [[ActionGirl Action Girls]] that Joukyuu is training.
* BlackComedyRape: Seriously. We're not talking about implicating or alluding to it either. Kunitoshi is a ''dick''.
* BreakableWeapons
* BroughtDownToNormal: Well, to at least half his power. Kunitoshi still manages to beat almost everyone without breaking a sweat.
* CharlieBrownFromOuttaTown: Akemi's boyfriend Daiki's going off the deep end, and Kunitoshi's the only one who might be able to stop him -- if he can get back into condition. He needs a sparring partner at his level, but Akemi doesn't think she can actively oppose Daiki. In the nick of time, the mysterious masked wrestler "Joan the Shadow" appears. (See PaperThinDisguise).
* CombatPragmatist: Kunitoshi, and he tries to teach his students to be ready for this.
* ComedicSociopath: Our questionable hero again.
* CoolShades: Daiki [[spoiler:which helps hide how he can barely see]].
* CurbStompBattle: Kunitoshi sometimes does this just to demonstrate his strength against anyone trying to buck the SortingAlgorithmOfEvil.
* [[DarkSkinnedBlonde Dark Skinned White Hair]]: Miu.
* DisabilitySuperpower: Daiki [[spoiler:is legally blind]].
* EvilMatriarch: Ayake Shinonome, Kunitoshi's mother and the one person in the world who can scare the crap out of him with her presence alone.
* {{Expy}}: Miu bears a strong resemblance (physically, if not in personality) to Sayuka from Isutoshi's previous series ''Slut Girl''.
* EyesAlwaysShut: Habu [[spoiler:until Kageyoshi one-ups her, at which point they open and stay open]].
* FakeUltimateHero: "Bull-kun"
* FigureItOutYourself: Kunitoshi ''never'' properly teaches his students, even when he's a ''college lecturer''. However, he does give legitimate praise and guidance when his students do learn.
* FingerPokeOfDoom: With 90% of his strength in his left arm, Kunitoshi is able to take out two members of an elite military martial arts squad by poking their foreheads.
* FlashStep: Being able to move faster than the eye follows is a sign that you're one of the stronger characters. On video, it looks like a stupid dance, [[spoiler:but Kizuki learned to pull it off by ''mimicking the dance'', earning some respect from Kunitoshi]].
* ForeignFanservice: Metara (The blonde [[TheGunslinger Gunslinger]] bodyguard of Kizuki).
* GenreSavvy: Kunitoshi loves {{lampshading}} Shonen tropes even while he's subverting them. Kunitoshi on the PowerOfFriendship:
-->"''Frieennds? So you're that kind of guy? Always singing the same old song. 'You're not alone.' 'If you have troubles we will be there for you.' 'Together we are strong.' Those kinds of songs, there are so many of them! (...) However... don't you think they say that just to cover their own incompetence? Isn't that just a means to cheer oneself for being poor and hopeless? 'Friends' is what you call someone who likes to be someone else's minion, isn't it? [[SlasherSmile I don't need such things like 'friends'! Well, I don't have any friends to begin with]]!"[[note]]Full disclosure -- he's saying this to the new BigBad's new QuirkyMinibossSquad to get their goat while deliberately giving his students a preview of what they'll be up against.[[/note]]
* GunsAreUseless: At least anything lethal.
** Averted in Chapter 64
* TheGunslinger: Metara
* HandicappedBadass: Kunitoshi can only usually tap into half of his full strength ever since his father ''dislocated and relocated half of the bones in his body'' in a vain effort to humble him. He regains part of his ability as the series progresses, but Kunitoshi himself believes he will never fully recover.
** Houju has rheumatism (pain/inflammation of joints/muscles) and cataracts (causes blurred vision) in addition to reduced physical speed and stamina from old age. He's still one of the strongest characters in the cast.
** Karasumaru temporarily became this as a result of injuries inflicted during his fight with Joukyuu, dropping under 50% of his former ability. He himself [[LampshadeHanging notes the irony]] that his condition is so similar to Joukyuu's. Both he and Joukyuu note he will recover in a few years.
* HeelFaceTurn: Miu, Akemi
* HeirToTheDojo: Kizuki
* HollywoodHealing: Whether they've taken a whip to the face, a large punch to the stomach, had a hand penetrated by a sharp object or breathed in poisonous gas, bandages heal everything.
--> "Geez, has my place become a field hospital?"
* IAmNotLeftHanded: Karasumaru's battle with Joukyuu is pretty much entirely going his way... until Joukyuu reveals that just because he's recovered to 70% of his old strength, it doesn't mean he's ''limited'' to 70%. Cue beatdown.
* IHaveYouNowMyPretty: One of Kunitoshi's [[BlackComedyRape worse habits]]. As most of his opponents are gorgeous, well-built young women, he occasionally wrangles it so he gets to have his way with them if he wins. [[ShowyInvincibleHero And he always does.]]
** Though in fairness the person did offer it up if he won the fight. Naturally he didn't waste any time beating her.
* ImprobableWeaponUser: Eventually this becomes more of a rule than an exception, from bizarrely shaped multi-bladed swords to circular three barreled guns and even more indescribable weapons. It seems that for many modern martial artists, getting an edge means developing a signature style too weird to be predictable.
* IncorruptiblePurePureness: Rin Kizuki. Particularly impressive, considering basically everyone else in town is a foul-mouthed brute.
* InstantSedation: Sometimes averted, sometimes not with Habu's poisons.
* JerkassHasAPoint: Kunitoshi's a jerk, but his advice is usually pretty good.
* KidSamurai: Akifumi Wado, one of Miu's QuirkyMinibossSquad.
** KatanasAreJustBetter: Kunitoshi makes fun of him for using a custom titanium blade instead of a ''real'' katana or bokken.
* LightningBruiser: Andrew, a product of an old Soviet science experiment to create someone super-fast, ultra-strong that feels no pain.
* MightyGlacier: Houmei's bulk makes her physically strong and extremely tough. The disadvantage to this build is lampshaded when it turns out that she bulked up too much to keep up with higher-end opponents, and sabotaged her own ability to use kung fu as a result. She actually has to slim down to be competitive again.
* MyKungFuIsStrongerThanYours
* {{Nepotism}}: Tenhou is thrown into a martial arts-focused school despite having no strength because his mother has high connections there.
* PaperThinDisguise: "Joan the Shadow," but no one buys it at all.
* QuirkyMinibossSquad: The Ten Knights
* RedBaron: Kunitoshi, called the "Gravity Magician". [[ For]] [[ good]] [[ reason]].
* RestrainingBolt: The entire first arc was spent with Kunitoshi slowly but surely easing most of his handicap, and even coming up with little ways to work around his restricted physical limitations.
* SchoolOfHardKnocks: Juzenji High; admissions at Ryobu University also depend on an applicant's martial arts skills, which drives some of the plot.
* ShownTheirWork: For all its ridiculousness, [=AIKI=] is actually fairly grounded in reality for a martial arts manga.
* ShowSomeLeg: Miu flashes Kunitoshi to set him up to be thrown. Unfortunately, he'd [[BatmanGambit positioned himself so he could bounce off a light pole in his flight path back at her]].
* SlasherSmile: Isutoshi appears to have a lot of fun drawing these.
* SmugSuper: The only reason Kunitoshi gets away with being such a cocky bastard is that he has the skills to back it up.
* TakeThat: During the fight between Houmei and Seiji Sawatari, Seiji breaks out his "[[RanmaOneHalf Cat Fist]]". Kunitoshi's reaction...
-->'''Kunitoshi:''' I know that the Chinese martial arts have 4000 years of history, but doesn't "Cat Fist" just sound too weird?
* ThatCameOutWrong: Seiji Sawatari (the Chinese Kempo fighter who humiliates Houmei) has a tendency for his expressions of bloodlust to come out the wrong way. For instance, when trying to challenge Kunitoshi:
-->'''Seiji:''' I'm here to screw with Joukyuu-san.\\
'''Kunitoshi:''' (Grimaces)\\
'''Seiji:''' Hold it right there, I'm not a homo...\\
'''Kunitoshi:''' Go kill yourself.
* TheStarscream: Habu became disgruntled with Daiki and in chapter 40 of the manga revealed her intention to take control from him. [[spoiler:She didn't get the chance to act on it.]]
* TheStrategist: Tenhou
* ThrowingOffTheDisability: Kunitoshi spends a good amount of time being injured in later arcs to avoid being a total BoringInvincibleHero, but readily curbstomps his opponent as soon as he recovers.
* TricksterMentor
* {{Troll}}: Some of Kunitoshi's more outrageous stunts are purely done to piss people off.
* TykeBomb: Habu, the poison-user.
** Andrew, the SuperSoldier who was engineered to be a superstrong LightningBruiser that feels no pain who is doomed to die young thanks to the side effects of the experiments performed on him. Even ''Kunitoshi'' feels a little sorry for him.
* UnsympatheticComedyProtagonist: Kunitoshi, very much. The audience is not expected to empathize with him in the least.
* WeakButSkilled: Kizuki's small stature but immense skill with throwing techniques qualifies her as this; she can't take very many hits and isn't that strong, but she moves pretty damn fast. To quote Joukyuu on the subject:
-->'''Kunitoshi:''' Power should just be the icing on the cake. If you utilize your opponent's power, even a little kid should be able to send a two-meter-tall wrestler flying. It's not easy, but it can be done... It's not power, nor is it speed.
* WhatTheHellHero: Everyone else in the series calls Kunitoshi out on his, well, everything, all the time. He never listens. When Bull-kun tries it in chapter 77, Kunitoshi turns it back on him by making him realize that he isn't any different.
* WhenYouSnatchThePebble: Kunitoshi challenges Kizuki to catch a small fish -- with one hand, ''slowly'' -- to prove that she's worth his time.
* WorldOfBuxom: A consequence of BoobsOfSteel being applied practically across the board.