One main story and then there’s a bonus story!
About a kindergarten teacher who disguises himself during then weekends and has one night stands, he has a one night stand with a straight man, and when he realizes this he gets angry and leaves the hotel. The next day, that straight guy comes to his kindergarten to pick his nephew out and realizes that he is the same guy he met on the weekend, he blackmails him to try out some anal toys that he has to review.
Shou Sensei no Ecchi na Himitsu