Jungkook-Yeseul's unexpected meeting during their vacation in Jeju-do lead to a short romance between those two. But due to an emergency, Yeseul did not manage to give Jungkook her phone number before they depart.

Summer Break ended! So, school has started. So, Han Yeseul is introduced as Jeon Jungkook's new class mentor. The student and teacher are both shocked. They cannot hide the fact that they actually liked each other since their last meeting in Jeju-do, yet they cannot confess due to their professional relationship. 

So what will happen to these two?