Yuu Koito

The protagonist of the story. A female student at Toumi East High School, in her first year. Born on April 5th. She is 152 centimeters tall. She lives with her father (Tetsuji, voiced by Ikiji Nose), mother (Ryoko, voiced by Yoko Imaizumi), older sister (Rei, voiced by Mikako Komatsu), and grandmother (Mitsuko, voiced by An Yao). Occasionally, she helps out at the bookstore run by her grandmother.

Her acquaintance with Touko leads her to become a member of the student council at Toumi East High School. Although her appearance is cute, her personality is cool. On the other hand, she is not good at making decisions and is aware of her own indecisiveness, making her weak to requests. Despite her small stature, she has high physical abilities due to her time in the softball club during middle school. Academically, she excels in humanities subjects like English and Japanese but struggles with sciences.

She has never been in love and cannot feel "special" emotions towards anyone. After confiding this to Touko, she receives Touko's affection and experiences her first kiss at a railroad crossing after school. Even then, she cannot feel special emotions and tries to reject Touko's confession, but ends up accepting her affection on the condition that she won't fall in love with Touko. As she spends more time with Touko, changes begin to occur in Yuu's heart, but due to her promise with Touko, she hides her true feelings while continuing their relationship.

Initially, Yuu is often swayed by Touko, but from the middle of the story, she starts to take the lead more often, and by the end, Yuu holds the initiative in her relationship with Touko. Throughout the story, she mostly refers to Touko as "Nanami-senpai," and after they officially start dating, she calls her "Touko-senpai," using polite language. However, in the final episode, when they are alone, she starts calling her "Touko" without using polite language.

In the student council play, she plays the role of a nurse. Initially, it was a minor role, but after Yuu and Koyomi revised the script, it became a significant role that changes the protagonist's (Touko's) perspective. Like Touko, who saw herself in the protagonist, Yuu also saw herself in the lover character in the play, leading to her first confession to Touko out of fear that their relationship might end.

In the final episode, she is a university student and no longer has the braids she had in high school. She continues her relationship with Touko but has not informed her family, except for Rei, about Touko. She still struggles with making decisions and is quite troubled about which university to attend and her future career, consulting Touko about these concerns.