Arisa Hibiki is the formidable grandmother of Haruo Hibiki and serves as the chairwoman of the private school in Kawagoe where the series takes place. She is a central figure in establishing the narrative's primary objective, as she offers her grandson a crucial opportunity for a professional comeback. Recognizing that Haruo, a talented but difficult conductor, has been cast out from the international music scene, Arisa presents him with a strict ultimatum: he must start a boys' choir at her school and lead it to victory in a national competition within a single year.

Personality-wise, Arisa Hibiki is portrayed as a shrewd and pragmatic strategist. While she provides Haruo with a chance to rebuild his career, her methods are not purely benevolent. She demonstrates a tendency to apply pressure and engage in calculated bargaining to achieve her goals, particularly when it comes to recruiting reluctant students for the choir. She understands how to manipulate situations to her advantage, ensuring that the choir gains the necessary members even when faced with resistance. Her character suggests a deep understanding of her grandson's capabilities and flaws, pushing him into a situation where his musical genius is forced to interact with the very social and interpersonal skills he lacks.

Her primary role in the story is that of an instigator and overseer. She sets the high-stakes challenge that drives the entire plot, creating the framework for the choir's formation and their journey toward the national tournament. As the school chairwoman, she holds the authority to make this arrangement possible. She also occasionally tasks Haruo with errands, such as searching for a specific type of candy, which often distracts him from the more mundane aspects of teaching and forces other characters, like the music teacher Rika Iijima, to handle the bulk of the instructional work.

Key relationships are central to her character. Her most significant dynamic is with her grandson, Haruo Hibiki. She acts as a mentor and a puppet master, providing him with a lifeline while simultaneously setting him a nearly impossible task that challenges his abrasive personality. She also has a functional relationship with the choir members, whom she helps to secure through her forceful and sometimes coercive methods, ensuring the club has enough participants to function.

Regarding her character development, Arisa Hibiki remains a consistent and steady force throughout the series. She is the fixed point around which the chaotic energy of the choir and her grandson revolves. Her motivations are clear from the outset, and she works persistently toward that goal, showing little significant change in her own personality or methods. There is no available information regarding her own personal development arc.

Her notable abilities lie not in musical performance but in her keen strategic mind and her authoritative influence over the school's affairs. She effectively acts as a producer for the choir, using her position and cunning to clear obstacles and forge the path toward the national competition, even if her methods are often underhanded or pressuring. No information is available about any other specific abilities she may possess.