Kim Seungyeon (You) happens to be in a three year relationship with your beloved boyfriend that you've met since the first day of freshman year. The two of you were what we would call high school sweethearts as everyone knew about your relationship, and had thought you two were the perfect couple.

However during your summer break your bestfriends Yerin and Yuju asks you to come to a BTS concert, and at the concert something rather strange happens as one of the members seems to have fallen for you. In fact he was your bias!

Will you stay with your boyfriend who you promised to be faithful to or completely live the dream of a fangirl, who ultimately wants to date their bias? who happens to be hiding a huge secret.