Because their father transfers to Sapporo, Todo Yuto and Todo Eirika begin to live alone. They are siblings but they are not blood related. When Yuto was a child, his mother died, and his father remarried. Because of this, Yuto had a new mother and a sister, Erika. His new mother was quite gentle and made a lasting effect on him, but she died, too. Living alone, Yuto and Erika begin to love as man and woman. However, Sayaka, Yuto’s art teacher notices their relations, and takes an interest in Yuto and what’s going on……