Keisuke Iwazaki presents a public persona as a respected and physically fit high school physical education teacher. Privately, he operates under the alias "Rapeman" within a vigilante service co-founded with his uncle, a former surgeon linked to organized crime. This enterprise, formally named Rapeman Services, provides unconventional resolutions to personal grievances under its operational motto: "Righting wrongs through penetration."

Clients engage the service to exact retribution against individuals perceived as wrongdoers, typically women characterized as morally corrupt or socially disruptive. Contracts involve scenarios like avenging jilted lovers, reconciling familial estrangements, or suppressing workplace conflicts. When fulfilling assignments, Iwazaki dons a specialized black leather mask shaped to evoke a specific anatomical form, deliberately forgoing lower-body garments.

His methodology employs sexual assault as punitive instrument. Should victims display unresponsiveness or pleasure, Iwazaki utilizes techniques called "M69 Screwdriver" and "Infinite Loop" to inflict pain and reinforce the act's punitive intent. Despite occasional regret over specific assignments, he completes every contract without exception.

Iwazaki's origins, formative experiences, and personal relationships beyond his uncle remain unexplored. His character shows minimal evolution across official media. Live-action adaptations occasionally depict him investigating client claims to verify a target's guilt, though this procedural element does not alter his operational methods or ethical framework. Throughout the franchise, he maintains unwavering commitment to his dual identities and self-appointed role, sustaining internal tension without development or resolution.