Masaru Aso is the laboratory assistant of geneticist Doctor Mochizuki. He is used in one of Mochizuki's experiments related to the creation of the Neo Organism, enabling him to transform into the grasshopper-like Kamen Rider ZO. He flees to the mountains and lapses into a two-year coma before he is awakened by a telepathic call to protect Hiroshi Mochizuki, the doctor's son. After an attempt to discover the meaning of his transformation at Mochizuki Genetics, Masaru senses that Hiroshi is in danger and saves the boy from Doras as ZO. Masaru then reveals himself to Reiko and her karate class. ZO battles Koumori Man to cover Hiroshi and Reiko's escape, but they are sucked into a pocket dimension by Kumo Woman. ZO saves them and kills Kumo Woman; Koumori Man snatches Hiroshi, with ZO in pursuit. After he saves Hiroshi, Masaru tells Seikichi that Mochizuki used him in his experiments. Refusing to believe it, Hiroshi runs off. Masaru finds him and fixes his watch, recognizing the melody which awakened him as he helps Hiroshi cope with the revelation. Koumori Man assumes Mochizuki's form to lure Hiroshi away, and Doras knocks Masaru unconscious. Masaru awakens when a grasshopper shows him where Hiroshi has been taken. Making his way to a complex, ZO kills Koumori Man. He finds Hiroshi and Dr. Mochizuki, learning that the geneticist was the one who woke him up and that the Neo Organism has been acting independently to become a perfect being. When ZO tries to fight Doras, he is absorbed by the Neo Organism and Doras uses Hiroshi to force Mochizuki to complete its evolution. The music from Hiroshi's watch keeps Doras at bay as ZO escapes from the monster, and Mochizuki sacrifices himself to destroy the pool. The complex self-destructs as ZO and Hiroshi escape. Leaving the boy with Seikichi, Masaru leaves for parts unknown.
Characters
Masaru Aso/Kamen Rider ZO: The hero of the story, Masaru was Doctor Mochizuki's assistant until Mochizuki experiments on him. Although he hates Mochizuki, Masaru eventually forgives him.
Hiroshi Mochizuki: A young boy who lives with his grandfather, Seikichi, and is targeted by the Neo Organism. Hiroshi longs to be with his father, who went missing years ago. As a memento, Doctor Mochizuki gave Hiroshi a pocket watch which plays music. Hiroshi is afraid of ZO at first, but eventually calls him onii-chan.
Doctor Mochizuki: A mad scientist who turns Masaru into ZO and creates the Neo Organism. Although he dreams of creating a "perfect lifeform", it turns on him. Mochizuki uses grasshoppers to telepathically contact ZO.
Neo Organism: A pool of living fluid which relies on its container for survival. It assumes the appearance of a deformed, egotistical, unemotional boy resembling Hiroshi. It becomes the grotesque, Kamen Rider-like Doras to find Hiroshi and force Dr. Mochizuki to complete its evolution into a perfect life form and destroy the human race and its imperfections. Doras can regenerate after injury, absorbing materials to upgrade itself. When Doras absorbs ZO, it becomes Doras Strengthened Form.
Spider Woman: A monster created by Doras, she is a four-legged spider who captures Hiroshi.
Bat Man: Another monster created by Doras, he is a black bat-like entity which can disguise itself as a human. As Mochizuki, it lures Hiroshi to its master's hideout.
"Hohoemi no Yukue" and "Ai ga Tomaranai", composed by Eiji Kawamura with lyrics by Akira Ōtsu, were sung by the Japanese group infix.
''ZO vs. J''
The S.I.C. Hero Saga story, published in Monthly Hobby Japan magazine from February to May 2005, contained a crossover with Kamen Rider J entitled Masked Rider ZO : ZO vs. J. In the story, the Neo Organism Doras obtains the Fog Mother's powers. It introduces the characters Red Doras Ver. 2, Doras Ultimate Form and Fog Doras.
Adaptations
drew a manga adaptation of the film. It takes some liberties with the plot, expanding the role of several characters, a different characterization of ZO and more-graphic violence. The manga includes short stories about Kamen Rider Black and Kamen Rider creator Ishinomori. The film was adapted into the video game and released in North America, despite the film's never airing there. Saban Entertainment spliced together footage from Kamen Rider ZO for its Masked RiderTV show, with the monsters used in some episodes. Doras became Destructosphere, and was the first monster sent by series villain Count Dregon in the opening two-part episode "Escape From Edenoi". Kumo Woman became Arachnida, appearing in the episode "Stranger from The North" and with a monster from the sequel Kamen Rider J. Koumori Man became Parasect and appeared in the episode, "Cat-Atomic".
