Yuu Koito initially holds an idealized and romanticized perception of love, influenced by songs and shoujo manga. She believes that love should be an intense, overwhelming experience, and when she does not feel this way, she assumes that she is incapable of falling in love. Even as her relationship with Touko Nanami deepens, Yuu struggles to recognize and accept her own developing emotions, repeatedly denying that what she feels is love.

Those close to Yuu, including her older sister, often remark on her indecisiveness. She has difficulty making decisions about her future and lacks strong personal aspirations or interests, despite displaying some natural athletic ability. However, when she commits to something usually at the encouragement of others she applies herself diligently. While she is dependable and hardworking, she rarely seems emotionally invested in anything she does. She generally remains calm and unbothered, even when faced with setbacks. One of the few exceptions to this is her relationship with Touko, which is one of the only aspects of her life that evokes strong emotional responses from her.

Yuu is highly considerate and often prioritizes the feelings of others over her own. Her reluctance to make decisions sometimes stems from this tendency, as she allows others to choose for her rather than asserting her own desires. This is exemplified by Natsuki, her friend from the softball team, who refrains from encouraging Yuu to attend a high school with a softball program out of concern that she might influence Yuu’s decision too much.

Despite her indecisiveness, Yuu is capable of being direct and blunt when necessary. She does not shy away from confronting others when issues arise, preferring open communication to resolve conflicts, as seen in her interactions with Sayaka Saeki.

As her relationship with Touko evolves, Yuu gradually begins to recognize her feelings. She initially hesitates to admit that she has fallen in love, reflecting on how deeply troubled she is by the fact that Touko dislikes herself especially when Yuu has come to love the very things Touko resents. After the student council play, Yuu realizes that in helping Touko become more open and accepting of herself, she has inadvertently lost the role of being the one “special” person that Touko confides in.

Yuu’s perception of love shifts further when she assumes that Touko has rejected her confession. She questions whether her lack of an emotional breakdown, in contrast to Akari, means that her feelings were never truly love. With Maki’s guidance, she comes to the realization that she does, in fact, love Touko.

Following a heartfelt conversation where they openly confess their love for each other, Yuu abandons her romanticized notions of love. In doing so, she makes one of the most significant decisions of her life embracing her feelings and becoming Touko’s partner.

Yuu Koito has brown eyes and paradise peach-colored hair in the manga, which appears as a deeper peach shade in the anime. She typically wears her hair in two small ponytails above her neck and has a distinct cowlick that stubbornly sticks out from her head. Yuu is relatively short in stature and becomes annoyed when others point out her height.

Yuu Koito attended middle school alongside her friends Akari Hyuuga and Koyomi Kanou. During this time, she was a member of the softball team, where she became close with her teammate Natsuki Sonomura. However, after graduation, Natsuki enrolled in a different high school, causing them to drift apart.

Following their middle school graduation, a male classmate who had been close to Yuu confessed his feelings for her. Expecting to experience the overwhelming emotions she had read about in books and heard in songs, Yuu was instead left unaffected. Realizing that she was unable to reciprocate his feelings, despite wanting to, she began to believe that she was incapable of falling in love. With this understanding, she chose to turn him down after entering high school.

The name Yuu (侑) can mean “urge (someone) to eat.” Her surname, Koito (小糸), is composed of “small” (小, ko) and “yarn, thread, string” (糸, ito). Additionally, Koito is homophonous with 恋と (koi to), which translates to “and/with love.” This wordplay is directly referenced in official works, most notably in the title of Light Novel Volume 2, Chapter 1—恋と、小糸 (Koi to, Koito), meaning “Love, and Koito.”