An Eye for an Eye and a Hole for a Hole.

Kenji, the young head of Kato yakuza organisation, just got out of the jail. He comes home and founds out the opposing Sawaki yakuza is invading Kato's territory. Sawaki recruited Ikeyama and asked him to kill Kenji, but Ikeyama was Kenji's lover who exchanged the cup of brothers in a jail.