Chisato Sumiyoshi, a second-year student at Takafuji Private Academy, presides over the Food Research Club, which she founded. Her childhood bond with the protagonist stretches back to their elementary school days, rooted in a friendship that weathers years of shared history. A deep-seated aversion to chocolate lingers from the loss of her younger brother, whose love for the treat intertwined it with her grief—a pain she confronts and overcomes, eventually reclaiming it as part of her healing.

When the student council election threatens to disband her club, Chisato pivots from leading casual culinary explorations to navigating political strategy. She spearheads the protagonist’s campaign for student council president, leveraging his candidacy to thwart reforms endangering the club’s survival. Her calculated decisions blend pragmatism with fierce loyalty, driven by a dual desire to protect both the club’s future and the bonds within it.

Her relationship with the protagonist shifts gradually from a tsundere dynamic—oscillating between sharp assertiveness and unspoken care—to a heartfelt romance. This transformation follows her emotional reckoning with her brother’s memory, dismantling walls built by unresolved grief. Tensions and alliances with peers like Mifuyu Kiba further complicate her journey, revealing layers of quiet rivalry and solidarity beneath their interactions.

Chisato’s growth centers on embracing vulnerability. Key milestones—revisiting chocolate as a symbol of reconciliation, choosing transparency in love—mirror her broader role in uniting peers against institutional challenges. Her resolve to act, both as a leader and an individual confronting loss, fuels collective resilience, anchoring the club’s struggles within a narrative of personal and communal perseverance.