The protagonist Yuuichi fails the entrance exam and is attending prep school. Around this time his father remarries and the family gains three new busty members the mature alluring mother Mifuyu, her gyaru eldest daughter Natsuki, and the subdued second daughter Akiha. Living together with three women becomes too titillating for Yuuichi, and combined with exam stress he can no longer suppress his libido. A mysterious package arrives containing a strange penlight that has the ability to put anyone under hypnosis. He begins using it on his new family members