Sōsuke Ajino, once a celebrated pianist, saw his career collapse following a car accident that shattered his left hand and claimed his fiancée’s life. Left with limited mobility in his hand, he abandoned both his piano—a custom instrument later found decaying in a forest—and the stage, retreating into solitude. His stern demeanor as an elementary school music teacher earned him the moniker "Ajino the Deathbringer" among wary students, a stark contrast to his former brilliance.

This reclusive existence shifted when he encountered Kai Ichinose, a prodigy who could coax music from the forsaken forest piano. Despite his reluctance, Ajino recognized Kai’s untamed talent and agreed to mentor him, confronting his own unresolved grief through the boy’s progress. His past achievements, including Japan’s Grand Prize win and a controversial clash with conductor Jean-Jacques Theroux after a Chopin Competition preliminary elimination, underscored the tension between his disillusionment with competitive accolades and his renewed purpose in cultivating Kai’s artistry.

Securing a role at Kiriyama Music Conservatory, Ajino prioritized nurturing Kai’s creative independence over technical perfection, steering him toward international recognition while rejecting ranking-driven pressures. Their bond deepened from transactional lessons to a shared pursuit of redemption, with Ajino channeling his regrets into ensuring Kai transcended poverty through music. Though mentoring rekindled his connection to the piano, he never performed publicly again. His austere appearance—medium-length black hair, black eyes, and a signature ensemble of white shirt, green trousers, green tie, and black jacket—mirrored the disciplined yet fractured soul beneath.