Since the early death of his parents, Takami Akitoshi has lived alone with his beautiful elder sister, Hitomi, while concealing his dirty desires for her. One day, a mysterious girl named Mina enters his room. She introduces herself as Death and explains that she came to take his soul because he had reached the end of his lifespan. Hearing his screams, Hitomi runs in and, after the situation is explained to her, asks Mina to spare him. Mina, moved by her earnestness, tells them that if Takami fathers a child within a week, she will let him live another 10 years. Hearing her condition, he turns his face to Hitomi...

With his stepmother dead, and his father transferred to another city, Yuto is living alone with his ample-bosomed step sister Erika. Temptation soon gets the best of them and they start indulging their forbidden passions. They also attend the same university and it’s not long before their equally ample-bosomed music teacher, Sayaka, discovers their taboo relationship. Sayaka begins falling love with Yuto and threatens to reveal his secret if he does not succumb to her needs. This twisted love triangle spells nothing but trouble and is bound for a surprising finale…