Tarumi, a childhood friend of Shimamura, formed a close bond during elementary school, exchanging affectionate nicknames like "Shima-chan" and "Taru-chan." Their friendship faded after enrolling in separate junior high schools, where rumors suggested Tarumi embraced delinquency through truancy and aimless wandering. Reuniting in their first year of high school during winter, Tarumi actively pursued reconnection, initiating calls and invitations to rebuild their fractured rapport.

Physically, Tarumi sports long brown hair in the anime, typically accessorized with a scarf and a soft demeanor, while the light novels describe her hair as pale citrus-colored. She harbors a passion for painting, dedicating herself to the craft post-reunion and eventually crafting an intricate portrait of Shimamura in their second-year summer.

Her personality blends self-identified rebelliousness with unwavering devotion. Persistent yet vulnerable, her attempts to reignite their bond clash with Shimamura’s deepening relationship with Adachi. Tensions peak at a summer festival where Tarumi accompanies Shimamura, unaware of Adachi’s watchful presence—an encounter sparking jealousy and emotional conflict. This moment crystallizes Tarumi’s unspoken romantic feelings, though her efforts face repeated rejection as Shimamura increasingly prioritizes Adachi.

By Volume 10, Shimamura’s confirmation of her romance with Adachi prompts Tarumi to openly weep, laying bare her unresolved anguish. Their narrative concludes with irreversible estrangement, leaving her unable to reconcile lingering affection with Shimamura’s commitment.

Tarumi’s name, merging “barrel” (樽) and “see” (見), symbolizes containment and perspective, mirroring her role as a foil to Adachi. Their contrasting expressions of affection—persistence versus restraint—highlight divergent approaches to unrequited love. Though her presence wanes post-Volume 10, Tarumi’s influence lingers in Shimamura’s reflections on past ties and evolving relationships.