Having to repeat his final year in Tsurugamine High School, Kotaro is drawn to Judo through the encounters he make with first-year students Kumi Mifune, Sanshiro Saigo and Daigo Daigo. Having lost to Kotaro, first-year Judoka Kumi Mifune endeared to learn the Karate discipline in order to defeat Kotaro. However, the ambitious delinquent Judoka Daigo captured her as a bait to take on Kotaro and take over his long-standing Kyokutan dojo. Sanshiro Saigo who happened to be with Kumi was taken as well and caused the Judo Club to be involved in the conflict with Kotaro.

With the return of many previous characters (though many of them just making brief appearances) such as Shikato Tenzen, Momotaro Ushirono, Teruhiko Tenkouji and Kyoushiro Inamori; mixed with the appearance of new characters such as the leaders of the male and female Judo Clubs; Toshihiko Iga who seemed to know Kotaro very well and Rumiko Mitsugi whose panties Kotaro and Tenzen could never "possess" respectively, the new arc of Kotaro brings him and Mayumi to the world of Judo filled with the familiar mix of comedy, ecchi, and martial arts.