After losing her mother, Yuki lived away from her parents' home. However, she decided to return to her parents' home where her stepfather and younger brother are for the first time in a long while. She was relieved to see her cute little brother, but she soon discovered a secret about them. Her stepfather was actually bisexual... Yuki decided to step in as an older sister to help her younger brother, who was treated as a sexual outlet by her stepfather...