Akio Yashiro, a violinist, experienced a pivotal early-career setback when overwhelming nervousness caused him to drop his bow mid-concert, resulting in public ridicule and his abandonment of performance. His despair lifted after Yukina Nanahara encountered him despondent on the concert hall steps and offered encouragement, reigniting his musical drive. This encounter propelled him to renown as a violinist and a teaching role at Saint Cecilia Girls Academy, an institution safeguarding magically imbued instruments against misuse.

Outwardly projecting sophistication and benevolence, Akio garners student admiration for his talent. Secretly, however, he harbors disillusionment-fueled ambitions. Having obtained Canonne—a demonic violin costing his conscience and soul—he plots to gradually wield its power, aiming to enslave the academy’s students and staff. His arc traces a shift from a failure-vulnerable artist to a calculating manipulator exploiting dark forces for dominance within the educational setting he ostensibly serves.