Yuu Satsuki is the diligent student council president of Kirameki High School, acknowledged for her academic excellence and leadership. Her responsibilities often keep her busy, frequently seen carrying documents across campus. Outwardly composed and striving for perfection in her duties and personal conduct, she is partly motivated by admiration for Shiori Fujisaki, a renowned Kirameki High alumna and relative whose legacy shapes Yuu's aspirations. Despite her poised exterior, she harbors subtle vulnerabilities, like a tendency to lose her way, revealed only to those close to her.

Her background shows a deliberate effort to follow Shiori's path, including the aspiration to confess her feelings under the Legendary Tree on her own graduation day, mirroring Shiori's romantic ideal. Yuu believed achieving perfection in all things would lead to that pivotal moment. However, during her actual graduation, she hesitated to confess to the protagonist, who is one year her junior, missing the envisioned opportunity. This failure prompted her to reevaluate the importance of traditions versus genuine emotions.

A year later, when the protagonist graduates, Yuu returns to Kirameki High and confesses under the Legendary Tree. She explicitly states that the specific timing or adherence to the legend matters less than her feelings for him, emphasizing that their connection transcends rituals. This act demonstrates her development from rigidly pursuing an idealized path to prioritizing authenticity and personal resolve over external expectations. It signifies her growth beyond her role model's shadow and acceptance of her own imperfections.