In a world where superpowered people are heavily policed by robots, an ex-con teams up with a drug lord he despises to protect a teen from a corrupt cop.

The fourth part in the series "Code Between Brothers". The story takes place in Fukagawa, Tokyo, at the beginning of the Showa era, where five players following the harsh path of a knight defeat a despicable Yakuza gang.

Shozo Hirono has managed to separate from the Yamamori family and create his own small family, and extend his circle of acquaintances. These new friendships include a powerful underboss of the Muraoka family, Noboru Uchimoto.

Repeatedly beat to a pulp by gamblers, cops, and gangsters, lone wolf Shoji Yamanaka finally finds a home as a Muraoka family hitman and falls in love with boss Muraoka's niece. Meanwhile, the ambitions of mad dog Katsutoshi Otomo draws our series' hero, Shozo Hirono, and the other yakuza into a new round of bloodshed.