Based solely on the provided details, Action Mask (originally Action Kamen in Japanese media, localized as "Ultra Heroi") is the protagonist of a fictional television series within the Crayon Shin-chan universe. He gained superpowers through advanced technology from a scientist while near death. His in-universe lore identifies him as originating from "Action Planet" (Akushon Sei), arriving on Earth to protect peace.

In the film "Action Kamen vs Haigure Maô," the antagonist Leotard Devil (Higure) steals Action Mask's primary artifact, the "Action Stone," preventing his return to his homeworld. To recover it, Action Mask orchestrates events for the human child Shinnosuke Nohara to obtain the rare Action Card 99, drawing Shinnosuke's family into a parallel world to aid in the conflict.

Action Mask's allies include Mimiko Sakura, frequently targeted by villains to lure or trap him, and Dr. North Kasukabe (Professor Kitakasukabe), a scientist supporting his missions. His primary antagonist is Meke Meke, an embodiment of evil depicted with a permanent cigarette. Action Mask employs signature techniques like the "Action Beam" and "Action Beam Ball" against adversaries.

During the film’s climax, Action Mask confronts Leotard Devil in challenges after Shinnosuke retrieves the stolen Action Stone. He combines forces with Shinnosuke to unleash a decisive "Action Beam," defeating the antagonist. Following this victory, he gifts Shinnosuke an Action Mask costume as a token of gratitude.