Gwangyejungdok

Seol Dan-A, an ordinary high school girl who fantasizes about being successful, is struggling to fit in with a group of kids after accidentally becoming friends with them. Then, Dan-A's 'first love', who has changed so much on the outside and inside that she is completely unrecognizable, transfers to the school, and the first love, who is trapped in memories of Seol Dan-A in the past, becomes creepily obsessed with Dan-A. It's a nightmare for Dan-A, who is barely adjusting to the group. To make matters worse, she also gets into trouble with the leader of the group, a delinquent...

(Source: Naver, translated)