For the past ten years, Baek Hayeon has been living in guilt for ruining the life of his love, Yoon Yihan. Because of this, he feels he has no right to object when Yihan wishes to continue their relationship despite getting married. At the same time, Yihan's cousin, Yoon Jinwoon, has been using their secret as leverage to get Hayeon to sleep with him since he also has feelings for him. Just when the lives of these three seem to have gotten so irreversibly tangled, Hayeon is sent ten years into the past before the biggest regret of his life occurred. Though he is determined to alter the course of this timeline and save Yihan's life, he wants to keep ignoring Jinwoon's blatant feelings for him. However, when Jinwoon offers to help Hayeon avoid the very cause of his problem, the two become entwined all over again…