Natsu ga Owaru

One day, Yui and Ko who are childhood friends and lovers have sex in the club room. However, it is threatened by the pervert teacher who was watching it, Yui who allows the body on the condition of muzzle. At first it was Yui who had a feeling of disgust for being fucked by someone other than Kou, but gradually her body began to feel pleasant. Eventually the secret hole in the back that has never been touched by her boyfriend will also be trained by a pervert teacher.