Mitsuru Hitokoe serves as the chief broadcaster of Nanba Prison, a role that places him at the center of the facility's internal communications and public events. He is a slim young man of average height, with short black hair and eyes that are typically hidden. He personalizes his standard guard uniform by wearing a longer jacket that reaches his knees, accented with a dark green belt and gold buckle.

His personality is lively, mischievous, and unabashedly noisy. He often irritates those around him with his constant chatter and playful teasing, but his upbeat energy also makes him a reliable source of entertainment. Despite a self-righteous streak, he is genuinely kind toward the prisoners, communicating with them openly and even offering extra rewards beyond the standard privileges given to the inmates of Building 13. He has a remarkable talent for narration and live commentary, frequently serving as the announcer for the prison's annual tournament and other special occasions. This skill, combined with strong intuition, allows him to pick up on subtle feelings or secrets that others try to conceal.

Mitsuru's motivations stem from a desire to keep the prison atmosphere lively and to support his colleagues in their duties. He enjoys his role as a commentator and seems to take genuine pleasure in interacting with both guards and prisoners. His most important relationship is his long-standing friendship with Hajime Sugoroku, the chief guard of Building 13. He often teases Hajime with silly jokes, and the two share a playful dynamic that suggests deep mutual trust.

In the story, Mitsuru functions primarily as a supporting character and occasional narrator, providing comic relief and bridging scenes with his commentary. He does not undergo significant personal development, remaining a cheerful, dependable presence throughout. His notable abilities are limited to his broadcasting and observational skills; he possesses no combat capabilities and relies on his voice and wit to fulfill his duties.