Onogami Shigehiko, a teacher at an all-girls school, is a man of love – of love towards beautiful young girls – and to this day he has managed to keep this hidden from those around by playing as Mr. Serious.

From the fear of losing his beloved career as a teacher, he has had to abstain from crossing the line with any of his students until now.

…Indeed, until now, until he met Kagarino Kirie, a mysterious girl of stunning beauty – it is this meeting that finally derails him into crossing that line, a line that was better left not crossed.