Kaizou Katsu

Voiced by: Takahiro SAKURAI 櫻井孝宏



Ever since Umi kicked him from a jungle gym on the playground back when they were children, former child prodigy Kaizou has turned into some kind of insane believer in anything mysterious. His favorite magazine is "Moo", a mystery mag and he believes about every conspiracy theory there is, e.g. he thinks world will end in 1999 and is convinced that the "Priority Seat"-sign on the train depicts an Alien.

After being hit by an anatomy model, Kaizou also is convinced he's been turned into a cyborg by Suzu whom he usually calls "doctor" 博士 (hakase).

Back when he still was a child prodigy, Kaizou attended "Genius Cram School" 天才塾 (Tensai juku) which he destroyed after turning insane. A lot of former Genius Cram School students still hold a deep grudge against Kaizou, and thus come to Torauma High School to find Kaizou and tak revenge.


On color pics, Kaizou's eye color is usually depicted as green. His hair is usually shown to be half grey half black.
Under his school uniform blazer, Kaizou usually wears a striped T-shirt (of which actually only the part visible below the blazer is striped). He also always wears a key/wallet chain on his trousers.


Spelled as 勝改蔵 (KATSU Kaizou) in Japanese. Katsu 勝 means "to win". Kaizou is spelled with 改, meaning "revision" and zou 蔵 meaning "possession" or "warehouse". Literally, you could interpret the name as "the winning one who holds revisions" or similar.
Kaizou is a pun on the word kaizou 改造, which means "remodeling" or "restructuring" - as Kaizou thinks he'd been made into a "remodeled person" 改造人間 (Kaizou Ningen) - a cyborg - this fits quite well. The last name Kaizou also one of the Kanji with which you can write "katte ni" 勝手に - which, as you know, is a part of the manga's title (though it's written in Hiragana there).
In the beginning of the series, people often thought the name had been taken from Tokugawa/Meiji-time military hero Katsu Kaishuu 勝海舟, but Kumeta officially stated this was not the case.


Kaizou lives with his unnamed mother, who looks extremely young. His father is a Ninja who always hides himself and thus can't be seen. Neither Kaizou himself nor his mother have ever seen Kaizou's father (Kaizou's mother was made pregnant by his father using some special Ninja technique °_°), though several schoolmates claim to have seen him and say he looks like his son.


Kaizou's usual way of speech is somewhat similar to that of Nozomu from Sayonara, Zetsubou Sensei.
Kaizou owns an identical looking key chain for every day in the week as well as numerous identically striped T-shirts.
Kaizou promised numerous girls (including Umi) to spend christmas with them every year.
Kaizou has also has been dating (and more) numerous girls in his life (even at the same time), including his teacher.

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