Kyōji Akatsuki is a third-year student at Ayanagi Academy and a member of the Kao Council, the elite group of students from the Musical Department who stand at the top of the school. Before rising to that position, he was originally part of team Tsukigami, and by the time he joins the Kao Council, he becomes the leader of his own team, Team Akatsuki, guiding his students with a strict but respected hand. Under his leadership, Team Akatsuki finishes second in the Newcomers' Debut Performance and again second in the Ayanagi Festival, successfully advancing through each stage to enter the Musical Department.

Akatsuki is characterized by a serious, intense, and confrontational demeanor. He is deeply committed to upholding the traditions and prestige of Ayanagi Academy and is not afraid to take direct action when he perceives those traditions are under threat. This makes him appear intimidating and unapproachable to many, but his dedication to the institution and his students is genuine. He values efficiency, discipline, and hard work, and his strict approach in guiding his team earns him respect from those he teaches, even if his manner is harsh.

His primary motivation throughout the story is rooted in a longstanding grudge against Itsuki Otori, a fellow member of the Kao Council. Akatsuki holds Otori responsible for something he did to Sougen Hiiragi years before the events of the series. This resentment leads him to view Otori as a threat to the school's traditions and to actively scheme against him. In the first season, Akatsuki works to have Otori removed from the Kao Council by appealing to other members, arguing that Otori's unorthodox methods are endangering the school's legacy. Later, when Team Otori attempts to hold a guerrilla performance at the Ayanagi Festival after their official stage is destroyed by a typhoon, Akatsuki orders a shutdown of the unauthorized show, attempting to enforce the rules and prevent what he sees as a breach of order. His efforts are ultimately thwarted when other students rally to support Team Otori, and he is forced to relent.

In terms of key relationships, the most significant is his adversarial dynamic with Itsuki Otori. Akatsuki is openly hostile toward Otori, attempting to pick a fight with him in episode eight. Otori, however, remains unfazed and calm in response, even inviting Akatsuki to have tea with him, which only deepens Akatsuki's frustration. He also works closely with his fellow Kao Council members, including Sougen Hiiragi, Tsubasa Hiiragi, Lion Christian Yuzuriha, and Sakuya Sazanami, though his willingness to involve them in his schemes against Otori shows that his personal grudge can override their collegial bonds.

Over the course of the series, Akatsuki's rigid adherence to tradition and his personal vendetta begin to soften slightly. When Team Otori's determination and passion win over the student body, even members of the Kao Council who initially supported Akatsuki's position are moved to help them. This forces Akatsuki to witness the power of the very spirit he was trying to suppress, though he remains a largely antagonistic figure who acts as an obstacle for the main characters to overcome. His development is subtle; he does not undergo a dramatic change in personality, but events do challenge his worldview and force him to accept outcomes he cannot control.

In terms of notable abilities, as a member of the Kao Council, Akatsuki is an accomplished performer and a highly skilled musician and actor. He has the talent and knowledge necessary to lead a team and to prepare students for the demanding Musical Department selection process. His primary strength, however, lies in his strategic and administrative capabilities. He is able to navigate the political structure of the Kao Council and to use the school's rules to his advantage in an attempt to remove Otori from power. His determination and refusal to compromise also make him a formidable opponent when he sets his mind to a goal.