The older brother who is sleeping with his two younger sisters first reaches out to the older sister, and the younger sister who is watching it estrus and asks the older brother for sexual intercourse. First group: An older brother and two younger sisters who usually sleep in a small room, but on days when their parents are away, they repeat forbidden incest. 2nd group: The younger sister who went on a hot spring trip with her brother and was in heat when she saw the two who devoured each other's bodies begged, "Do you want me?"