The brother he hated to death is dead. A story of those left behind, unknown to anyone. 'Hyunwoo' loses his brother in an unexpected accident. 'Hyunwoo' learns that his homeroom teacher 'Yeonjeong's brother is the cause of everything. Meanwhile, 'Yeonjeong', who is going through a difficult daily life due to the accident caused by her brother, hears an unexpected story from 'Hyunwoo'. "Isn't the teacher's brother in prison?" 'Yeonjeong', who is flustered, receives an incomprehensible request from 'Hyunwoo'... "I want to go to the sea with you, teacher."