Cleavage - Episode 1

When their father leaves for work, Todo Yuto and Todo Erika are left to live alone. They are brother and sister, but they are not blood relatives. When Yuto was a child, his mother died. His father remarried a woman who already had a child from a previous relationship, Erika. His stepmother was very affectionate, but she too had already died. Living alone, they begin to love each other as boys and girls. However, Sayaka's teacher notices their relationship...