Onna no Iji(1971)

2 years ago, Kumi broke up with Shuhei and decided to forget everything about him for good. However, after being told that her younger sister, Junko, fall in love with a man and is currently living with him. She was determined to discover who was the man who won her sister's heart. But what will happen when she found out that the man in question is Shuhei, her first love?