An Ode to Yakuza (1970)

Tatematsu Minoru, a yakuza belonging to the Ishikawa group that runs the Shinjuku area, has a beautiful sister named Akane. He dreams of sending her to college and turning her into a perfect young lady. He's extremely fond of Akane. His fondness for her goes beyond how he feels about his mistress, Kanae. And yet, Akane feels alone. Now, a new tutor comes into her life that seems to have taken a liking to her...