Their father lives in Sapporo, so Todo Yuto and Todo Eriki live alone. They are children of the same parents, unrelated by blood ties. When Yuto was a child, his mother died and his father remarried. This is how he got a new mother and a sister, Erika. The mother was kind to the boy, but soon passed away as well. Living together, Yuto and Erika begin to love each other as man and woman. However, Sayaka, Yuto's art teacher, takes notice of their relationship, and she has her own sights on Yuto...