After Natsusa Yuzuki’s return to the team, Yuu Mashiro is first seen watching one of his videos with enthusiasm. During a training session, however, Yuu collapses and later wakes up beside Natsusa, who explains that his fainting was likely caused by anemia. Yuu admits that he feels behind the other team members and is determined to train harder to catch up. In response, Natsusa teaches him phrases to use when interacting with senior teammates to earn their support.

Yuu is later taken to the hospital, where he is diagnosed with anemia and a gastric ulcer brought on by malnutrition and stress. Frustrated, he laments his inability to play alongside Natsusa and the others. Natsusa reminds him that, despite being unable to play rugby himself due to injury, he still loves the sport. He challenges Yuu to reflect on whether he loves rugby enough to endure setbacks and hardships, pointing out the difficulty of becoming a regular given the strength of the team. When Yuu admits that he truly loves rugby, the moment marks a turning point in his resolve.

The following day, Yuu announces to the team that he will take on the role of manager, allowing him to remain involved with rugby while continuing to support his teammates.

Yuu Mashiro is portrayed as a young man with a noticeably slender and delicate build, which sets him apart from the more robust physiques of his teammates. His frame reflects both his physical frailty and the health struggles he faces, such as anemia and malnutrition, making his design visually consistent with his role in the story. His gentle facial features and youthful expression give him a softer presence compared to the other players on the Doshisha University rugby team.

He has medium-length blue hair, worn down with neat V-shaped bangs that frame his face, and a small ahoge that adds to his youthful charm. His green eyes further highlight his mild and approachable appearance. While his overall look conveys fragility, it also emphasizes his sincerity and determination, qualities that influence his interactions with teammates and his eventual role as a manager.

Yuu Mashiro is depicted as a shy and reserved first-year student who deeply admires Natsusa Yuzuki. His original aspiration was to play rugby alongside his teammates, but health complications caused by malnutrition and stress resulting in anemia and a gastric ulcer prevented him from pursuing that path. Despite these setbacks, Yuu continues to stay involved with the team, demonstrating resilience and quiet determination.

He looks up to Natsusa for guidance and often follows his advice, including tips on how to communicate with senior teammates. Yuu is easily flustered, particularly when receiving praise for his efforts, yet he consistently strives to do his best in supporting the team. His gentle and kindhearted nature makes him approachable, and even players with colder or more difficult personalities are shown to respect him and rarely go against his requests.

Overall, Yuu’s personality combines humility, warmth, and dedication, making him a valuable presence within the team despite his inability to contribute directly on the field.

Natsusa Yuzuki
Yuu admires Natsusa deeply, looking to him as both a mentor and a source of encouragement. After Yuu collapses during training, Natsusa guides him through his health struggles and helps him find confidence in himself. Natsusa’s advice, including how to communicate with senior teammates, has a strong influence on Yuu’s development. Their bond is central to Yuu’s decision to remain part of the team as a manager rather than leaving rugby altogether.

Teammates
Although Yuu is younger and more physically frail than most of the Doshisha University rugby team members, his sincerity earns him their respect. Even the colder or more stubborn players respond positively to his kindness, making him effective in his role as manager. His interactions with the team highlight his growth in confidence and his determination to contribute despite his limitations.

• The given name Yuu (優) can be translated as “excellence,” “superiority,” or “gentleness,” reflecting qualities of kindness and refinement.
• His surname Mashiro (真白) combines ma (真), meaning “real” or “genuine,” and shiro (白), meaning “white.” Together, it can be interpreted as “truly white” or “genuine purity,” imagery that aligns with his gentle personality and delicate appearance.