Satsuki Shinonome is a diligent second-year student at Takafuji Private Academy, initially serving as head of the student council's Financial Affairs Department. Her pragmatic approach leads her to propose disbanding underperforming clubs, aiming to reallocate funds toward reforming the school's financial aid system. This controversial policy stems from her underlying concern for equitable resource distribution, seeking to reduce the burden on scholarship students facing discrimination and lengthy work obligations. Standing 163 cm tall with a slim build, she has brown waist-length hair styled in a hime cut with blunt bangs, green eyes, and measurements of 85-58-84 cm with a D-cup bust.

Her personality blends charisma, political savvy, and strong motivation, earning her a significant student following and an honorable reputation. Though initially competitive with her election rival, Yūki Ōjima, a chance encounter sparks romantic feelings. She expresses this through playful teasing and nicknames, yet ultimately acknowledges his bond with Chisato Sumiyoshi and supports their relationship. Following the election, she accepts the role of Student Council Vice-President, collaborating with President Yūki to implement shared goals and integrating into the group she once opposed by joining the Food Research Club.

Her family manages a traditional wagashi (Japanese confectionery) shop, influencing her fondness for sweets, and she commutes to school by bicycle. A central aspect of her background involves a strained relationship with her older sister, Hazuki Shinonome, a teacher at the academy. This tension, rooted in unresolved family issues surrounding Hazuki's birth and upbringing, initially fuels Satsuki's resentment. However, she reconciles with Hazuki after learning the truth about her sister's past, leading to mutual understanding. Her development concludes with her diligently supporting the student council while maintaining a cordial, unrequited connection to Yūki. Her given name "Satsuki" means "May".