Masaki Mizushima, known professionally as the Normal Hero Manual, is a professional hero based in Hosu City. He is a brown-haired man in his late twenties whose hero work centers on routine public safety duties such as patrolling and traffic management, rather than high-profile combat. His hero name reflects his personal philosophy that it is better to be competent in many areas than to specialize in a single talent. This belief drives him to handle any task thoroughly and reliably, making him a figure of quiet dependability rather than flashy spectacle.

Manual possesses an unnamed water-manipulation Quirk that allows him to control and redirect pre-existing sources of water. He cannot create water from nothing, so he must rely on available liquids such as hydrants, pipes, or other reservoirs. The Quirk has a noted weakness to air pressure, which can disrupt his control. He has demonstrated the ability to change the trajectory of water gushing from fire hydrants to extinguish flames, and he has also been seen coating his hands and arms with a liquid-like substance, suggesting a degree of direct control over fluids. During the Paranormal Liberation War, his Quirk proved essential for a subtle but critical support role: he continuously replenished Eraser Head’s eye drops to counteract dry eyes, enabling the hero to maintain his vision-blocking ability.

Personally, Manual is described as kind, attentive, and ordinary in demeanor. He is sensible and considerate, earning high praise from colleagues and citizens for his sense of responsibility. He aspires to be a role model for modern heroes, embodying the idea that consistent, reliable service is as valuable as spectacular feats.

In the story, Manual first appears as the work-study mentor for U.A. High School student Tenya Iida during the Hero Killer Stain arc. He quickly perceives that Iida’s choice of agency is motivated by personal revenge against Stain, the enemy who injured his brother Tensei. Manual confronts Iida with a firm warning that a hero must never use their Quirk or position for personal vendettas, regardless of the justification. This guidance marks a key moment in Iida’s moral development. Beyond this mentorship role, Manual participates in the larger conflict against the Paranormal Liberation Front, contributing as a support hero rather than a frontline combatant.

Manual’s key relationships are limited but meaningful. His most prominent connection is with Tenya Iida, whom he mentors with a balance of warmth and stern principle. He also works alongside other heroes in Hosu City, blending into the network of pros who handle everyday heroics. His development is subtle: he remains a steady presence throughout the series, never seeking the spotlight but proving his worth when unusual circumstances demand his specific talents. His costume has a fishman-like design, which complements his water-based abilities and adds to his distinctive but understated visual identity.