Now a high school girl, Saya is beginning to realize that her family has a strange relationship that is different from others. It is a family where incestuous sex between her father and her brother, and between her brother and her mother, has been a normal part of her life. Furthermore, both her father and brother cum inside her, so even though she feels uneasy, when they get involved, her sexual desire is aroused out of habit and she ends up having sex. At such times, even if her mother is right next to her, she does something else as if nothing is happening. This relationship has continued for a long time.