They were originally a pair of wounded souls, unconsciously warming each other. She deeply knows that she is just a substitute. His heart belongs to someone else, and what she is waiting for is just going their separate ways after a year. He also understands her identity as a substitute. Countless times, he has rescued her from hardships. He originally thought that he would never fall in love with anyone in this life. However, why does his heart ache so much and be so panicked when she disappears?