Boss of the Underworld (1959)

Ryuta and Mineo Komatsu are brothers, both yakuza (gangsters). Mineo, although complicit in crime, even murder, wants out of the gangster life, hoping to become a successful singer instead. Ryuta loves his brother, but Mineo's possible defection presents problems for the gang, and Ryuta realizes he must kill his brother if he wants to survive.