Masaru Aso is the protagonist of the 1993 tokusatsu film 'Kamen Rider ZO,' which is part of the Kamen Rider franchise. As a former assistant to the scientist Dr. Mochizuki, Masaru is transformed into Kamen Rider ZO after being subjected to experimental procedures. He awakens after two years of hibernation and takes on the role of protector, fighting to save Dr. Mochizuki's son, Hiroshi, from the monstrous Neo Organism. ZO's journey is that of redemption and heroism, embodying the classic Kamen Rider spirit.