A guy and his younger sisters have sexual fantasies-which is completely normal for their ages-. But the important fact is that they have naughty sexual fantasies about the sisters or the brother. They ignore this and simply think they are perverted and have sinful desires. Until one day they found out about the others feelings and all hell breaks lose in the house. And the girls decide to please the otaku-like desires of the brother by dressing as his favorite anime and eroge characters.