Kazuhiro Hasukawa, eldest brother to Kazuya, shouldered guardianship after their parents’ untimely death in their youth, juggling Kazuya’s upbringing with his academic endeavors at Ryokuto Academy. His marriage to Sumire—Kazuya’s former tutor and unrequited first love—fractured their bond, driving Kazuya to seek solace in Greenwood dormitory. Despite the rift, Kazuhiro’s fierce "Papa Wolf" protectiveness emerges whenever Kazuya faces emotional harm, underscoring his unwavering dedication.

Serving as Ryokuto’s school nurse, Kazuhiro adopts a casually teasing yet observant stance toward his brother, discreetly monitoring Kazuya’s welfare through his role. Though he permits Kazuya space to mature independently—even tolerating mentors like Mitsuru and Shinobu—he intervenes sharply if their guidance threatens Kazuya’s stability.

The union with Sumire initially shattered Kazuya’s idolization, fueling betrayal and disillusionment. Yet Kazuhiro’s steadfast support and subtle nudges gradually mend their relationship, fostering Kazuya’s growth. His marriage, marked by genuine affection and mutual respect, silences baseless speculation about his motives or sexuality.

Shaped by childhood abandonment and the burdens of premature responsibility, Kazuhiro’s loyalty and familial devotion remain unshakable. His quiet involvement during Greenwood crises—Mitsuru’s kidnapping, Kazuya’s health scares—reveals a guarded care for the dorm’s eccentric residents. He anchors the chaotic environment with approachable authority, blending reliability with understated command.

Kazuhiro’s arc subtly shifts from surrogate parent to trusted confidant, balancing Kazuya’s autonomy with silent vigilance over his safety. His past beyond raising Kazuya and building a life with Sumire remains unchronicled, solidifying his role as a stabilizing pillar within the series’ comedic and dramatic tapestry.