Ryo Ueki is a high school student attending the same school as Ritsuka Uenoyama. He has been friends and classmates with Ritsuka and Shogo Itaya since their first year of junior high. The trio regularly spends breaks at the school basketball court, later including Mafuyu Sato.

Ueki possesses short, messy blonde hair and golden eyes. He typically wears a red jacket over a white T-shirt, switching to sleeveless tops and dark shorts for basketball.

He exhibits a calm, collected personality, often appearing less talkative than others while maintaining a friendly demeanor towards classmates like Mafuyu Sato. Ueki frequently adopts a no-nonsense approach toward Shogo Itaya's energetic behavior, physically restraining Shogo by the head when he becomes overly disruptive.

During basketball practice, Ueki participates alongside Ritsuka, helping him up after a fall and questioning his distraction. In class, he observes interactions, including Shogo sharing Ueki's personal art project without permission despite Ueki's futile attempts to stop him. He witnesses exchanges between Ritsuka and Ayano Kasai and agrees to attend Mafuyu Sato's live band performance with Shogo, sharing an interest in music.

He attends the concert venue where Ritsuka's band performs, noting it is his first time there and observing the crowd size. During Mafuyu's performance, he looks around at the audience reactions.

His given name, Ryo, derives from the Japanese character meaning "refreshing". He is approximately 17 years old during the main events. Ueki enjoys playing basketball and has an interest in music, particularly live performances.

Ueki maintains a close friendship with Shogo Itaya, frequently seen together during school activities and basketball. He interacts with Ritsuka Uenoyama both in class and during sports. Through these connections, he becomes acquainted with Mafuyu Sato and shows support for his musical endeavors by attending live performances.