After getting married three years after a romantic relationship at work, Rinko is a wife who lives with her husband Yu, her younger sister, who has moved to Tokyo to become a photographer. Yu was a little younger than Rinko and was kind to her like a real sister. One day, my husband decided to leave the house on a business trip for three days. Under one roof, two step-sisters are alone. Normally, women could live together without any worries, but Yu had a secret that he couldn't tell anyone. Yu had been in love with Rinko from the day they first met...