Also in the flowering season of youth, one person lives in the sunshine and the other lives in the darkness. A small grudge, an agreement made together, ended up with two completely different results. She never forgets her old love, and pity becomes her eternal fault. She becomes a puppet and loses all her memories, but only remembers that love. But she, whom he treats like his biological sister, actually comes here for him! Gratitudes and resentments intertwined, love, hate and sorrow, he supported her and helped her, but he never expected to cause an uproar...