Bukiya Musou - Kabukichou No Kaibutsu-Tachi

Bukiya Musou Kabukichou No Kaibutsutachi Manga :

Kabukicho—a city rampant with murder, robbery, assault, and theft. Amid the chaos, a "weapons dealer" provides tools for survival. Tosa, a handyman renowned as Kabukicho's strongest, runs an orphanage for children without parents, just like himself. Though poor, he lived a happy life with the children until a conflict with an anti-social organization robbed him of his most precious bonds. Devastated and consumed by rage, Tosa embarks on a quest for revenge. To curb his recklessness, the informant Mitsuki introduces him to a man: Kai, the "weapons dealer" of Kabukicho. The fateful meeting between the handyman Tosa and the weapons dealer Kai sets the city in motion—a gritty hard-action tale set in Kabukicho!