New Battles Without Honor and Humanity 3: Last Days of the Boss
新仁義なき戦い 組長最後の日 (original)
Nozaki, a labourer who swears allegiance to a sympathetic crime boss, only to find himself elected his successor after the boss is murdered. Restrained by a gang alliance that forbids retributions against high-level members, Nozaki forms a plot to exact revenge on his rivals, but a suspicious relationship with his own sister taints his relationship with his fellow gang members
Starring Bunta Sugawara, Chieko Matsubara, Kōji Wada, Kenichi Sakuragi, Takeo Chii, Isao Bitō, Koji Nanjo, Takuzō Kawatani, Keiko Kinugasa, Harumi Sone
Watch "New Battles Without Honor and Humanity 3: Last Days of the Boss" on Amazon released in 1976. It's a action & adventure and crime movie, and has a rating of 6.8 out of 10 from Imdb which is usually fine for this kind of movie, and is currently only available for purchase or rent.