Taehyung who suffer from depression always heard a girl's voice everytime he tried to commit suicide. One night her voice was heard in his dream and made a bet with him that she will save his life. Tomorrow morning, she appeared in his school but that girl doesn't even know what Taehyung was talking about. 

Krystal who just come to study in her new school and suddenly some of the girls in her class force her to confess to someone that she don't even know. What will happen after that?