A male student with short, wavy white hair. After Go Jutae's death, he drifted apart from his close friend Park Seolah and lived an ordinary life as a teacher. One day, he thought to himself, "I want to go back," and was actually transported to the past. During his original school days, he was a flawless model student, but because of that, he failed to be there for Jutae when he was struggling and lonely. Now that he has returned to the past, he takes great care of Jutae and is very warm and considerate. He is the same age as Seolah and one year older than Jutae.

A female student who returned to the past along with Lee Seobaek. She has long black hair with slight waves at the ends. Before returning to the past, she worked as a police officer. She is quite skilled with her hands, and her ability to pack lunch boxes is extraordinary. She has a kind and warm personality and often wears her hair tied up. She is one year older than Jutae and the same age as Seobaek.

The male student who is the catalyst for the loop. He has short black hair that slightly reveals his eyebrows and a visible fang on the right side of his mouth. He is a friend of Lee Seobaek and Park Seolah, one year their junior. Unlike Seobaek and Seolah, he has looped hundreds of times, but every time he returns to the past, he inevitably dies on December 31st—the day he first took his own life. Whenever Jutae dies, everyone caught in the loop is sent back to the day of the entrance ceremony. He suffers from school violence and appears to have a difficult family life. Despite this, he enjoys spending time with Seolah and Seobaek after returning to the past. His personality is easygoing yet affectionate.

A male student who, like Go Jutae, has been through the loop hundreds of times. He has beige hair with bangs that cover his eyebrows and wears piercings in his ears. He has known Jutae since elementary school. While he may come across as rude or abrasive, he is a warm-hearted boy who only wishes for Jutae to be happy. He is the same age as Jutae and one year younger than Seolah and Seobaek.