Katte ni Kaizō is a shōnen manga by Kōji Kumeta. The manga ran for 26 volumes in Shōnen Sunday from 1998 to 2004. The art style went through a huge change as the story went on, by the end of the story the art style was the same as the type used in Kumeta’s next series, Sayonara Zetsubō Sensei. An anime adaptation by Shaft was released from May to October 2011.