Haruki Nakayama, a 22-year-old graduate student, balances academia with his role as bassist and de facto leader of a band, where his tall, slender frame and layered outfits—often paired with a distinctive purple bass guitar case—make him a recognizable presence. His honey-blonde hair, initially long but later cropped short, frames almond-shaped eyes and a goatee, occasionally accompanied by subtle stubble.

Beneath his cheerful, approachable demeanor lies a perceptive mediator skilled at resolving band conflicts and managing public relations. Though adept at reading others’ emotions, he masks his own insecurities about his musical talent behind casual humor, prioritizing others’ needs while privately wrestling with obsessive tendencies toward his passions. His quiet longing for bandmate Akihiko Kaji, unreciprocated for years, complicates their dynamic until shared vulnerability shifts their relationship.

A veteran of disbanded groups, including one fractured by tensions with ex-girlfriend Aya, Haruki co-founded "The Seasons," handpicking its members and anchoring their sound with his prized Japan-exclusive Fender Jazz Bass. His resilience is tested as past failures haunt him, yet he gradually embraces emotional openness, particularly during a charged period of cohabitation with Akihiko. Their tentative bond solidifies when Akihiko, motivated by self-growth, confesses mutual feelings.

Notable quirks include a July 13 birthday, blood type O, an aversion to ghosts, and a fondness for French New Wave cinema. The kanji for "spring" in his name mirrors his evolving journey, while practical details—a van (license plate 580 22-58) and merchandise featuring cigarettes and fried rice—nod to pivotal story moments, grounding his narrative in tangible authenticity.