Empire of kids (1981)

Following a stint in reform school, Ryu (Shinsuke Shimada) returns to his home, the Minami area of Osaka, accompanied by his new friend Ko (Takeshi Masu). He's greeted by his friends, Chabo (Ryusuke Matsumoto) and Ken (Bang-ho Cho). They seek to forge their own path through a multitude of rival gangs in Kita and Minami, including the Hokushin Alliance, backed by the yakuza, the Hope Association, and various other minor factions, including Zainichi Korean groups. What follows is a wild, fast-paced story of violence, revenge, betrayal, and discrimination, that never loses its sense of humor.