After returning home to Tokyo after a long absence, Takashi was excited to see his sister Mary again. He couldn't believe how sexy she had become since he last saw her. Innocent and naive, Mary didn't seem to understand that her lack of a boyfriend in Tokyo made her an easy target for Takashi's advances. When he heard that she would go back to being a virgin if they didn't have sex for a while, he knew he had to take advantage of the situation.