Most of the movie is shot in documentary-style and all fight scenes are created using CGI. The "documentary" crew follows Masaru Daisatu (Hitoshi Matsumoto), the last protector of Japan and the sixth person in his family to serve in such a capacity. When jolted with electricity, he is able to grow to giant proportions and he works for the Japanese defense ministry to defeat giant monsters when they attack the cities. Although Daisatu generally defeats most of his monstrous foes the vast majority of Japanese citizens either regard him with apathy or consider him a bigger threat than the monsters he fights (and some show greater sympathy to the monsters than him). Further, he has been forced to wear advertisements as he does his job and he is constantly harangued for failing to attract big ratings for his televised battles. He lives in squalor and his ex-wife only lets him see his daughter twice a year and regards him as a freak.
After defeating one monster, Daisatu is ambushed by a mysterious Red Monster who breaks his nose and forces him to run away. Daisatu refuses to face the monster again, even though doing so would boost his popularity. Eventually, the Japanese government sneaks into Daisatu's house while he is passed out drunk and shock him, forcing him to grow and fight the Red Monster (which, it is discovered, is from North Korea). During the fight, Daisatu accidentally kills his grandfather who had grown to giant size to help him, and Daisatu once again attempts to flee. The Red Monster catches him and again beats him to a bloody pulp.
At this point, the film cuts to "live footage." Instead of being in CGI, Daisatu and the Red Monster are actors fighting in a clearly fake Japanese town, reminiscent of Power Rangers or Ultraman. A family of robotic-looking giant super heroes (decked out in US colors - earlier in the film Daisatu noted that he was apathetic towards America) arrives and easily humiliate and defeat the Red Monster. They ask Daisatu to join them in the fight, but he realizes that his presence there is nothing more than symbolic as they are just as powerful without him. Having defeated the Red Monster, the robotic family convinces Daisatu to accompany them as they fly victorious into the sky. During the credits, Daisatu sits at a dinner table with the robotic family as they argue with each other about why they were not able to defeat the Red Monster more efficiently and with more style.
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