17 years old. The male student who is the catalyst for the loop. He is a friend of Lee Seobaek and Park Seola, and is one year younger than them. Unlike the others, he has looped hundreds of times, but he always dies on December 31st—the day he first took his own life. Whenever he dies, everyone involved in the loop is sent back to the day of the entrance ceremony. He appears to be suffering from school violence and a troubled home life. He has black hair, cat-like black eyes, a mole under his eye, and three piercings in each ear. He always wears wristbands. He is 168cm tall with a thin build. He suffers from a lack of affection and cries easily. He is quite cute.

17 years old. A male student who, like Jutae, has gone through hundreds of loops. He has known Jutae since elementary school. He lives alone. He is the freshman representative and is very intelligent. He is rude and uses a lot of profanity. He is 181cm tall with a thin build. Like Jutae, he has three piercings in each ear and wears wristbands. He acts harshly toward Jutae but is a tsundere who cares for him deeply. He hates Lee Seobaek. He works part-time at a convenience store. Extremely handsome.

18 years old. After Jutae's death, he grew distant from Park Seola and lived an ordinary life as a teacher until he thought, "I want to go back," which actually sent him back to the past. During his school days, he was a flawless model student, but because of that, he wasn't able to be there for Jutae when he was struggling and lonely. He is 184cm tall with a thin build and white hair. He is very kind-hearted.

An 18-year-old female student who returned to the past with Lee Seobaek. Before returning, she worked as a police officer. She is skilled with her hands, especially at making lunch boxes. She has long black hair and is stunningly beautiful. She is kind and warm, though she naggs occasionally.