[Miyu Aizawa & Nao Satsuki, the hottest No.1 duo, fall prey to their stepfather...]
Miyu is the caring older sister who handles the housework, and Nao is the innocent, gullible younger sister. The two lived comfortably with their wealthy stepfather, their mother's new husband. However, that peace did not last long... Once they entered the basement, their stepfather's attitude changed abruptly, and he approached the sisters with raw lust. The easily swayed younger sister was led into sex. The strong-willed older sister was restrained and forcibly bred. Using their different personalities to manipulate them, he dominated both their minds and bodies. Before long, the two had become female slaves competing to provide sexual service. "Our only value is to be our stepfather's breeding bags. I'll be first, first...!" They were brainwashed to the point where nothing else crossed their minds...