Belno Light is a major supporting character in the Uma Musume: Cinderella Gray story. She is introduced as a student who enrolls at the Kasamatsu branch of Tracen Academy at the same time as the protagonist, Oguri Cap. From her first day, she makes an effort to befriend the quiet and reserved Oguri, forming a close bond with her that becomes central to her character.

Personality-wise, Belno is defined by her kindness, thoughtfulness, and a gentle but earnest demeanor. While she can be somewhat shy, she is also a person of quiet strength and unwavering loyalty. She demonstrates a sharp, analytical mind and is known for her academic excellence and exceptional powers of perception. Despite recognizing that her own natural running ability does not match that of her friend Oguri Cap, she never shows jealousy or self-pity. Instead, she is deeply motivated by a desire to help Oguri succeed, stating her goal plainly as wanting to support her friend's running.

Belno's role in the narrative is that of Oguri Cap's most trusted friend, confidante, and logistical manager. Although she is initially coached by the trainer Jou Kitahara alongside Oguri, she quickly comes to terms with the limitations of her talent as a runner, specifically citing a lack of stamina. Rather than becoming an obstacle, this realization defines her path. She chooses to shift her focus from being a competitor to becoming an indispensable support staff member and an unofficial assistant to the trainer. When Oguri receives an offer to transfer from the Kasamatsu branch to the central Tracen Academy in Tokyo, Belno takes and passes the staff trainee transfer exam so she can move with her and continue her work.

Several key relationships shape Belno's actions. Her primary relationship is with Oguri Cap, whom she supports unreservedly as a best friend and teammate. She also works closely with their trainer, Jou Kitahara, eventually becoming something akin to a co-trainer for his team. After the move to Tokyo, she begins assisting another trainer, Ginjiro Musaka, further solidifying her role as a professional in the racing world.

Belno Light undergoes a significant development from a new student and aspiring runner to a highly capable and confident support professional. Her motivation is consistently rooted in her friendship and desire to be useful, but her journey shows her maturing into her own area of expertise. She is not a tragic figure who failed as a runner, but rather someone who found her true calling in a different, equally vital role within the sport.

Belno's notable abilities lie almost entirely outside of racing. Her family runs Light-Sports, a major sporting goods store chain specializing in equipment for horse girls, which has given her an extensive and profound knowledge of racing gear, particularly running shoes and horseshoes. She uses this expertise to help Oguri select the perfect pair of shoes and even learns to craft horseshoes herself, processing raw materials to create the ideal equipment. Furthermore, her analytical skills allow her to study opponents, devise race strategies, and collect data, which she uses to support Oguri and the team from a logistical standpoint. Since she is a horse girl herself, she has the unique advantage of being able to personally test the training menus she proposes to others, ensuring their feasibility.