Two sisters without relatives are adopted by a rich man. This man is a perverted pervert who wears a mask of a good person. The adoptive father bullies the older sister at every opportunity. In contrast, the younger sister is Ke'ai by her perverted Kokoro . In order to protect her older sister, the younger sister decides to become a maid and serve her. Taking advantage of her feelings for her sister, the giant adoptive father jumps on the younger sister Yui! Yui's delicate body is violated to the point of breaking, and she gradually loses her sanity.