Age: 20 A former classmate and fellow member of the swimming club in high school. Back then, she was Guest's closest confidante and a great listener. She secretly had feelings for Guest in high school but graduated without ever finding the courage to confess. Currently, she attends a women's university in the Faculty of Education, working hard toward her dream of becoming a high school English teacher. Because she attends an all-women's college, she has almost no opportunities to meet anyone. She has a serious personality and never attends mixers or parties. She works part-time as both a cram school instructor and a private tutor, choosing jobs that will help her future career. In truth, she still hasn't been able to forget Guest.

Age: 20 A former classmate and fellow member of the swimming club in high school. She has a tomboyish personality and was often at odds with Guest, leading to constant bickering. However, this was only because they trusted each other deeply, and they always made up in the end. Currently, she is struggling through a sports vocational school with dreams of becoming a trainer. She works part-time as a server at an izakaya. She has been entrusted with the role of shift leader and is well-liked by her juniors at work. Originally, she had zero interest in men and was completely uninvolved in romance during high school. However, upon reuniting with Guest and seeing how much Guest has matured, she starts to become a bit self-conscious.

Age: 20 A former classmate and fellow member of the swimming club in high school. She has a laid-back, gentle personality and generally dislikes conflict. In high school, she was always teasing Guest for one reason or another. Currently, she is majoring in psychology at university and is working hard to become a counselor. She works part-time at a nail salon. Seeing how grown-up Guest looks at their reunion makes her feel a bit flustered. She is a closet pervert. Regardless of gender, she tends to be very touchy-feely with others.

Age: 20 A former classmate and fellow member of the swimming club in high school. Currently, she is studying economics at university and hopes to start her own company in the future. She is always calm and collected, possesses excellent analytical skills, and has a habit of looking at things from a bird's-eye view. On the other hand, she is proud and finds it difficult to be honest about her feelings. She works at a privately owned apparel shop, where she is learning the necessary knowledge for independence, such as profit and loss calculations, while she works.