Joukyuu is an expert martial artist, renowned for his prowess in the art of grappling and throws. About ten years before the start of the series, the bones in his body were dislocated and relocated overnight by his father, who wanted to teach Joukyuu a lesson about humility.Despite this, Joukyuu still retains the majority of his technical skill in martial arts, as well as his crass, self-serving, perverted nature.
Arrogant Kung-Fu Guy: Through and through, with the caveat that he has earned the right because he is an extremely difficult opponent to fight. It only gets worse as his body begins to recover.
Awesomeness by Analysis: Skilled at dissecting the weaknesses and strengths of a particular fighter's style even if he's never encountered it before.
Handicapped Badass: He may still be ambulatory, but attempting to use too much of his strength at once will cause his bones to dislocate themselves (such as when he used his Raijin techniques against Karasumaru).
Break the Haughty: His father's decision to dislocate his joints was an attempt at this. It didn't take.
Jerk with a Heart of Gold: It's extremely hard to find, but whenever he offers even the slightest bit of advice to his "disciples" or assists them in a roundabout way (such as breaking Mei's fight against Sarutari into rounds, so that she wouldn't be totally decimated in one long brawl), it shows through.
Older Than They Look: The primary difference between Joukyuu at 16 and Joukyuu at 26+ is the fact that he's dyed his hair and got some bags under his eyes. Otherwise, he looks exactly the same. He gets rid of the dye by the time he's seen in Aiki S.
Picky Eater: If it's not Japanese food, you'd better bet he'll make a fuss about having to eat it, let alone look at it.
Power Limiter: The dislocations in his body, which are gradually fixed as the manga goes on thanks to Mei's grandmother or injuries he receives from swords.
Red Baron: Is known as the "Gravity Master" due to his expertise in throwing techniques.
Sink-or-Swim Mentor: For the most part. He will give an occasional hint, and maybe a demonstration, but that's about all; he's otherwise perfectly willing to let his "disciples" get the snot kicked out of them to figure out what he's trying to teach them.
Weak, but Skilled: In comparison to his old self, who had power, speed, and technique; he's kept the last two (and in fact has improved on his technique, since he's been forced to use his strength conservatively). This slowly becomes less of an issue as his body continues to recover.
The granddaughter of the school board's chairman; a third-year student at Juuzenji High. Her grandfather asked her to watch over the school in his absence.
Lead The Target: The primary skill that Metara has yet to learn, which is what hampers her ability to fight.
Wandering the Earth: Left Juuzenji for a while when she realized that she wasn't strong enough to protect or fight alongside Kizuki. Returns partway through the first arc.
A gym teacher at Juuzenji, and one of Kizuki's bodyguards. Uses Kung Fu; in the past, she used her style's powerful internal strikes to compensate for her lack of muscularity, but has chosen to develop her physical strength instead.
Mighty Glacier: Deconstructed. Joukyuu and Mei's grandmother both point out that she has thrown away her flexibility and technique in favor of pure power, which works against her actual style of fighting.
Took a Level in Badass: When she comes back from her training trip with Metara, she's slimmed down and demonstrated that she can utilize internal strikes again.
Wandering the Earth: Left Juuzenji for a while when she realized that she wasn't strong enough to protect, or fight alongside, Kizuki. Returns partway through the first arc.
Joukyuu's cousin and the daughter of Juuzenji's principal. A third-year student, and the top martial artist of the class, she wants to enter Ryobu University, and initially approaches Joukyuu in order to enlist his help in fighting against Kizuki.
Amazonian Beauty: She is depicted as an attractive woman with a muscular yet lean and curvaceous build. Usually, she wears a bra-top underneath a short leather jacket that allows her to flaunt her defined and well-toned abs.
Flash Step: Not only can she use Joukyuu's Thunder Step, but she can combine it with rapid jutte strikes to attack from multiple angles.
Insistent Terminology: Even when Joukyuu's being the scummiest of scum, she will call him sensei/master without fail.
The greatest swordsman still living in the world, despite his advanced age. He and his family become the targets of a terrorist named Veronica and her organization because they're in possession of the legendary sword, Heaven.
Handicapped Badass: As noted on the main page, he's got cataracts and is rheumatic, which basically cripples his eyesight, power, and speed all at once. He's still more than a match for pretty much anyone else in the series, Joukyuu included.
Picky Eater: He greatly dislikes the European food he's been living on for a while, and greatly prefers Japanese food.
Weak, but Skilled: His great age has definitely affected him a lot, but he's more than good enough to compensate for it.
Joukyuu's father, and thus, the one responsible for limiting Joukyuu's physical strength.
Combat Medic: In Joukyuu's own words, Tatsukuni was a middling martial artist, but had extensive knowledge of the human body.
Posthumous Character: By the time the series has started, he's dead. He has made an appearance in one flashback and is infrequently referred to by the other characters, usually in the context of Joukyuu's disability.