The morning sun streamed into my bedroom... One day, I woke up with a hangover and noticed a woman's hand touching my body. Thinking it was my wife, I followed the hand and turned the covers over my head, only to be greeted by an unbelievable sight. My wife's younger sister, Yui, who came to stay with us since yesterday to look for a job, was sleeping there completely naked! "This is bad... this situation is really bad..." I somehow managed to get out of the situation without my wife finding out, but since then... Yui has been trying to seduce me when my wife isn't looking, as if to play with me...