Three years after getting married at the end of a workplace romance, Ririko, a wife who lives with her husband's younger sister, Yuu, who has moved to Tokyo with the aim of becoming a photographer.Yuu was a little younger than her Ririko, and she loved her like a real sister.One day, her husband left her house on a business trip for three days.Two sisters-in-law alone under one roof.Originally, women should be able to live together without worrying about each other, but Yu has a secret that he can't tell anyone.Yu has been in love with Ririko since the first day she met him.