S1, E1: Susin High School is a top school reserved only for the top 0.1% of students in the nation. The precious 8-day winter vacation is about to begin. Everyone else has left campus but 7 students, who have each received an anonymous letter, have decided to remain. Meanwhile, a victim of a car accident, a psychiatrist by the name of Kim Yohan, discovers Sushin High and receives help. Then, after the school is blocked off by the first record snowfall in decades, the students begin to search for the sender of the letters...