In 2017, world leader Friend has turned Tokyo into a walled city, an oasis in a world ravaged by a vicious flesh-eating virus. Friend continually issues a prophecy that the world will end in August of 2017, and that only “true believers” will be saved. Otcho, now an old man, fights his way back into Tokyo and attempts to track down Kanna. Kanna is Kenji’s niece; Kenji was the first person to recognize Friend for the villain he was, but has been presumed dead for seventeen years. Otcho reunites with Kanna, and plays a song for her on the radio, written by Kenji. Kanna has learned the song by heart, but the radio plays a different version of the song with new lyrics. They both realize that Kenji must still be alive. Meanwhile, Maruo, another member of the resistance, tracks down Kiriko, Kanna’s mother. Kiriko has been in hiding since Kanna was an infant, working to undermine Friend’s plan to release a super virus on Japan in August. She and Friend are Kanna’s parents, although at the time Friend used a false name, so Kiriko does not know his true identity. She tests a vaccine on herself, which proves successful in protecting her from Friend’s new virus. She has Maruo pack up a supply of the vaccine to take to Tokyo, where the virus will be spread.

A mysterious man arrives at a border checkpoint, where he meets Manjome. Manjome is an elder advisor to Friend, but has been exiled to the checkpoint in recent years because he knows too much. The stranger identifies himself as Kenji, who survived the events of December 2000, although he suffered amnesia in the process. Only recently did he recover his memory, including the true identify of Friend. Manjome pleads with Kenji to kill Friend and save the world; Kenji agrees to save the world, but on his own terms, and heads to Tokyo. Kanna and Otcho are apprehended by Friend’s military police. Otcho breaks free and discovers that Friend has constructed flying saucers and another giant robot for dispersing the virus. What’s more, the robot has a neutron bomb in its core. Kanna is brought up to meet Friend. Friend hints that his own rough childhood brought him to his current state of sociopathy, and hopes that by making the world smaller people will be kinder to each other. He releases Kanna to rejoin her resistance.

Kanna realizes that Friend will spread the virus everywhere except the World Expo grounds, a perfect recreation of the 1970 Expo that occurred during Friend’s childhood. Kanna and her resistance decide to put on a music festival to attract as many people to the expo as possible, where they’ll be safe from the virus, touting the return of Kenji, whose song has become an underground hit. A large crowd assembles while Friend releases the virus. Otcho arms himself to take out the flying saucers. Kenji arrives in Tokyo and pursues the giant robot, boarding it and causing it to stumble onto its side. When Kenji emerges he is confronted by Friend. Friend unmasks himself and is revealed to be Fukube, who was thought dead in the same night as Kenji in December 2000. Kenji, however, declares that he is only pretending to be Fukube, and that he knows his true identity. Kenji apologizes for wronging Friend during their childhood; he stole a toy badge from a snack shop and Friend was mistaken for the thief. Friend panics and tries to reboot the robot, but is shot by Manjome. Manjome himself is crushed by the falling robot. Kenji arrives at the festival, where he reunites with Kanna and all his childhood friends, and plays his song for the crowd.