Song Jaeyoung, a typical high school student, is perplexed when Kang Yihan, a mysterious classmate, suddenly breaks down in tears at the sight of him. Following this encounter, Jaeyoung's life takes an unexpected turn as Yihan begins sticking close by, offering his help with an unusual sense of familiarity. As strange events begin to unfold around him, Jaeyoung grapples with the growing question: Can he truly trust this enigmatic boy who seems to know him so well?