Mr. Saenai, whose full name is Hideo Saenai, is a 52-year-old middle-management salaryman working for a construction company. He is an ordinary office worker by day, but his life is upended when a mysterious old man forcibly hands him a super suit and pressures him into becoming a reluctant superhero. Saenai is an everyman character defined by his unremarkable, middle-aged existence, struggling with the pressures of his job and a domineering wife, Enko, at home. His personality is pragmatic, weary, and somewhat passive; he does not seek out heroism and often grumbles about the inconvenience of his new duties. His primary motivation stems not from a grand sense of justice but from a sense of obligation and the practical need to handle immediate crises, especially those involving his family. The core contrast in his life is the tension between his mundane domestic and work responsibilities and the extraordinary, often absurd, superhero tasks he is forced to undertake.

In the story, Saenai serves as the main protagonist. His role is to navigate everyday troubles and occasional criminal threats while attempting to maintain a normal family and professional life. He is caught between the demands of world peace—in the form of petty crimes and disasters—and his chaotic home life, where his wife Enko is a formidable presence. He is married to Enko, who is described as a wife from hell, and they have two adolescent children, a daughter named Haneko and a son named Moyao. His relationships are marked by this domestic conflict; he is weak-willed and submissive at home but must be assertive as a hero. Over the course of the series, his development involves a reluctant acceptance of his dual life and a gradual, often comedic, exploration of what justice, peace, and happiness mean for an ordinary man with extraordinary power.

His notable abilities are granted by the super suit. He can fly at high speeds, possesses immense strength capable of punching through rocks and demolishing structures, has X-ray vision allowing him to see through walls or clothes, and can exhale with enough force to blow away opponents. A key property of the suit is a light emission that causes anyone who witnesses his heroics to forget his activities within seconds, preventing his identity from being discovered but also robbing him of any recognition. The suit can be folded into the size of a handkerchief for easy carrying and can detect when it is needed. Despite these powers, his life does not improve simply by becoming a superhero, and the story focuses on the mundane and humorous challenges that arise from this predicament.