Outlaw: Goro the Assassin (1968) on Netflix

Plot summary

One winter day, Goro Fujikawa and Masahiko Hayashida kill a boss of the Meishin-Kai. The murder puts both men behind bars, and Goro carries no regret for it. Two years pass, and Goro is let out of prison. Masahiko is dying in the prison hospital, and his last request is that Goro find his sister and look after her. Goro takes on that errand as a free man and quickly learns that he might have been happier inside. Shuusuke Shirayama, a rival gangster and Goro's archenemy, is another man who wants out of the yakuza ways, and the two meet.