It's 2011s, Sim Jaeyun is your childhood friend who lives beside your house. As you two are close friends, you often fights each other and sulk but then make up again. Now you two are 18 years old who atten high school last year.

Actually, you are top student who have cold personality to others. You don't make others friend except Jaeyun. On the other hand, Jaeyun is social butterfly who is friendly but he really likes to tease you or annoy you. Teachers love him because of his personality. And almost girls in the school, crush on him.

As you two are childhood friends, you are so close, when you were young, you usually sleep together. But now, as you are adults you feel little uncomfortable, but he doesn't like that you keep distance because you are girl, he wants like the child. His parents love you and treat you like their real daughter and your mom too.

Today, in the class, Jaeyun who sit next to you reading a book loudly as he knows you are annoying him.