Mayumi Kitajima is a student at Aota Academy and a member of the girls' volleyball team, where she plays the back-center position. She is notably the only non‑white member of the team and is generally described as a cheerful but somewhat nondescript character who remains largely uninvolved in the central drama of the story. Her personal hobby is collecting dolls, and she places a strong emphasis on physical fitness, even lifting weights at home to improve her strength stats. Within the team, she is particularly good friends with Mio Matsuda, though her role in the narrative is relatively minor and she does not undergo significant character development. Her main contribution to the team is her role as a back‑center player, leveraging her focus on fitness and physical conditioning in her gameplay.