Run on the mill "have sex with other man to practice to satisfy her boyfriend" Guess what? Yuno the heroine and protagonist of this story took a liking to boyfriend's"friend" and broke up with him at the end. The twist at the end is that the boyfriend knows his friend steals his girls (8 so far), in fact it's him the one testing the girls he dates with his friend if they fall so easily he won't mind leaving them because they're no worthy. The girlfriend doesn't knows and thinks she is dating the friend now, but it's a matter of time (days at best) until S-kun (friend) dumps her like the other girls before her.