Momoko Hyakushiki is the chief warden of Nanba Prison, a male correctional facility in the world of Nanbaka. She is a tall and statuesque woman, standing at 181 centimeters, with long blue hair and red eyes. Her physical presence is commanding; she is notably taller than many of the male characters, such as Enki Gokuu, and can easily pat his head. Momoko exudes an air of dignity and authority that can be intimidating to those around her.

Her personality is stern, serious, and somewhat sadistic. She possesses a frightening glare and an intimidating aura, which she uses to maintain order and discipline within the prison. She takes her job as warden very seriously and is fully committed to her duties. Despite this harsh exterior, Momoko harbors an unrequited romantic affection for Hajime Sugoroku. She finds him handsome and cool, but her feelings are not reciprocated; Hajime perceives her as suspicious and is unnerved by what he views as her death glare. This one-sided love adds a layer of complexity to her character, contrasting her otherwise formidable demeanor.

As the chief warden, Momoko plays a crucial role in the story, overseeing the prison’s operations and interacting with the inmates and guards. She is a supporting character whose presence reinforces the strict hierarchy of Nanba Prison. Her key relationships include her subordinates, such as Hajime Sugoroku, and the inmates under her watch. She commands respect from those around her, though her romantic feelings for Hajime create an awkward dynamic.

Throughout the series, Momoko’s development is subtle. She remains consistent in her authoritative role, but glimpses of her vulnerability regarding Hajime are occasionally shown. Her notable abilities lie in her leadership and her capacity to project power and control, which she uses to manage a facility housing some of the most dangerous criminals. While specific combat feats are not highlighted, her status as warden implies a level of competence and strength necessary for the position.