Having failed his university entrance exams, Atsushi has become what people call a hikikomori. Unable to bear the situation any longer, his father asks his colleague's wife , Haruka, to be his private tutor. Although Haruka has experience as a private tutor, she is at a loss when it comes to Atsushi's lack of motivation. So Haruka comes up with a plan to get Atsushi to concentrate on his studies... It's a dirty lesson using her own hands and mouth. And the extreme lessons gradually escalate...