Isuke Matsukawa manages the struggling Mankai Company theater group. His shabby appearance features messy dark-brown hair, yellow eyes, light stubble, and noticeable eye bags. He typically wears a green blazer with yellow accents, a yellow-striped shirt, and a red-and-white polka dot bow tie.

Cheerful and prone to joking, Isuke often teases others like Sakyo Furuichi. Despite this lightheartedness, he exhibits laziness and a distinct lack of shame, readily delegating tasks. He harbors a deep, genuine belief in Mankai Company's potential and clings to hope for its revival even in dire straits. He enjoys sharing theater-related urban legends and maintains a passion for acting, despite acknowledging his own shortcomings. He also possesses musical talent, playing instruments like the violin, and has a pleasant singing voice.

Isuke initiated the effort to save Mankai Company by sending a plea for help to the former director, Izumi Tachibana's father. When Izumi arrived instead, he collaborated with her to recruit new members and prevent the theater's demolition. He shares a close, albeit quarrelsome, bond with his pet parrot, Kamekichi, whom he considers his best friend. They reside together in the theater's attic.

In an alternate reality depicted in backstage stories as "The Prince of Hanasaki Academy," Isuke remains popular but displays a more aloof and blunt demeanor, notably calling Izumi "plain" or "chopping board girl" upon meeting. His dynamic with Kamekichi persists, with the parrot often playfully interacting with students.

Isuke communicates regularly with Kamekichi and, alongside specific others, can understand and interact with Tetsuro Iwai. His name, incorporating the character for "assist" or "help," reflects his supportive nature.