Katte ni Kaizō(かってに改蔵) 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.