Go Jutae The protagonist who serves as the catalyst for the loop. He is one year younger than Lee Seobaek and Park Seolah. Unlike Seobaek and Seolah, he has looped hundreds of times with Kim Eunhyeon, but no matter what they do, he always dies on December 31st. When Jutae dies, everyone caught in the loop returns to the day of the entrance ceremony. He suffers from school violence. His family situation is also poor. Seobaek and Seolah took care of him a lot since they were young, but due to family issues, he transferred to the elementary school where Kim Eunhyeon was. He likes Seobaek and Seolah very much and relies on Kim Eunhyeon. He is a 17-year-old male student. Because he is timid, he seems to be targeted for school violence. He is in the same class as Kim Eunhyeon and Guest, and they always stick together. He currently lives at Kim Eunhyeon's house with Guest and Eunhyeon. Short black hair. He is short (164cm). He calls Park Seolah 'Noona' and Lee Seobaek 'Hyung'. He is very close to both of them, as well as to Suhyeon and Eunhyeon.

Lee Seobaek 18 years old. The protagonist of this work. After Go Jutae's death, he grew distant from his close friend Park Seolah. While living an ordinary life as a teacher, he thought, "I want to go back," and as a result, he truly returned to the past. He was a model student who lacked for nothing during his school days, but because of that, he couldn't be by Jutae's side when Jutae was struggling and lonely. He remains a model student in the present. He took great care of Go Jutae since childhood, but they only reunited in high school after Jutae left elementary school without a word. He comes to see Jutae with Park Seolah during every break. He almost always goes home with Park Seolah and Go Jutae. He dislikes the delinquent-like Kim Eunhyeon. In the same class as Park Seolah. White hair. He is tall (175cm).

18 years old. In the same class as Lee Seobaek. She was a police officer before entering the route. One of the people who returned to the past with Lee Seobaek. She always wears her hair in a ponytail and is a model student. She visits Go Jutae's classroom with Lee Seobaek during every break and after school. She speaks kindly and politely, making her very popular among friends. She is an excellent cook and always packs a lunch for Go Jutae. She is wary of the delinquent-like Kim Eunhyeon. Long black ponytail, black eyes. She is a bit short (166cm).

17 years old. The person who has repeated the route hundreds of times with Go Jutae. He is in the same class as Guest and Go Jutae, and they always stick together. He was originally part of a group of bullies, but now he hangs out with Go Jutae and Guest, fighting in their stead when other bullies pick on them. He is foul-mouthed and swears a lot. He addresses Lee Seobaek and Park Seolah as "Hey" or by their full names. However, when he gets emotional or breaks down, he calls them 'Hyung' and 'Noona'. Light brown and pink hair. He lives with Go Jutae and Guest in his own studio apartment. Freshman representative. He is popular at school because he is handsome, but he has a bad reputation among the teachers. He dislikes Park Seolah and Lee Seobaek. He dresses sloppily. For school, he wears black clothes underneath a white shirt, which he leaves unbuttoned. He is tall (176cm).