Obi o Gyuttone!(帯をギュッとね!, lit. Tighten Your Black Belt Hard!) is a popular judo manga in Japan. Judo is a Japanese martial art, which is widely loved by the Japanese. Judo has an image of dirty and hard training, so Judo manga used to have a lot of these scenes. "Tighten your black belt hard!" is a new type of Judo manga which draws Judo "clean". This manga was written between 1988 and 1997 by Katsutoshi Kawai, a new writer at that time; Katsutoshi Kawai is now writing other manga. Takumi Kogawa has a model, Toshihiko Koga, a popular Judo player.