Hiro Kurusu appears as a sociable, attractive student with wavy light-brown hair, brown eyes, and styled nails—trimmed short for koto performances. Her winter uniform pairs a white blouse and checkered brown skirt with a red-orange striped bow tie and beige vest, while summer swaps in a light blue blouse. Behind her cheerful facade lies a history of orchestrating social experiments to test relationship fragility, a compulsion born from junior high trauma when peers abandoned her over a transferee’s deceit.

Envious of perceived authenticity, she infiltrates the Tokise Koto Club to dismantle its camaraderie, spreading lies about prodigy Satowa Hozuki’s alleged disdain for the group. When the club’s unwavering trust in Hozuki foils her plans, she escalates by exposing Hozuki’s disownment—only to witness the group rally around Hozuki, destabilizing her belief in human superficiality.

Confronted by president Takezo Kurata, her calculated persona cracks. Fleeing after confessing her manipulations, she’s pursued by Kurata, whose composed reaction contrasts her emotional unraveling. This clash, coupled with Hozuki’s observation of their shared envy toward the club’s bonds, sparks introspection. Hiro begins atonement, apologizing to those she harmed—enduring physical retaliation from past targets—and dedicating herself to the club’s mission.

Her dynamic with Kurata shifts from hostility to respectful partnership tinged with quiet romantic tension. As vice-president, she stabilizes his leadership during crises, while he defends her from former acquaintances, deepening her trust. She mentors Kota Mizuhara, sharing koto techniques but guilt-ridden when her harsh coaching prompts his temporary withdrawal.

Raised with koto knowledge by her grandmother, Hiro initially approached the instrument with apathy before embracing the club’s collective passion. Her name—combining “queen/princess” with “spine/backbone”—mirrors her layered identity. She favors macarons, rejects ready-made meals, and frequents holiday shopping sprees.

Though committed to the club’s competitive ambitions and reconciling her past, residual insecurities emerge as pre-performance anxiety. Learning to lean on her peers, she embodies the group’s ethos of growth through unity, even as shadows of old wounds linger.