Bringing her boyfriend home was a bold decision by the younger sister, even though she knew that her older sister Hatsukawa was famous for being a seductive woman with eyes that captivated boys. The younger sister's boyfriend was no exception; with his seductive actions and sexual assertiveness, he was easily enchanted by her. Even though they knew it was wrong, the secret meetings behind the poor younger sister's back made both of them feel delighted, as it created a sense of mystery and novelty for them. But in the end, the most pitiful one was still the younger sister, whose boyfriend was cheating on her while she pretended to be cheerful, unaware of the terrible things happening to her.