is a 1963 Japanese tokusatsu science fiction film directed by Ishirō Honda, with special effects by Eiji Tsuburaya. Produced and distributed by Toho, it is based on The Undersea Warship: A Fantastic Tale of Island Adventure by Shunrō Oshikawa and The Undersea Kingdom by Shigeru Komatsuzaki. The film stars Jun Tazaki, Tadao Takashima, Yōko Fujiyama, Yū Fujiki, and Ken Uehara. The film was released in Japan on December 22, 1963, and in the United States in 1965 via American International Pictures. A two-episode anime OVA titled Super Atragon, based on the same novels, was produced by Phoenix Entertainment in 1995. Plot The legendary empire of the lost continent of Mu reappears to threaten the world with domination. While countries unite to resist, an isolated World War II captain has created the greatest warship ever seen, and possibly the surface world's only defense. While on a magazine photo shoot one night, photographers Susumu and Yoshito witness a car drive into the ocean. While speaking with a detective the next day they spot Makoto Jinguji, daughter of deceased Imperial Captain Jinguji, who is also being followed by a suspicious character. Her father's former superior, retired Rear Admiral Kusumi is confronted by a peculiar reporter, who claims contrarily that Captain Jinguji is alive and at work on a new submarine project. The threads meet when a mysterious taxi driver attempts to abduct Makoto and the Admiral, claiming to be an agent of the drowned Mu Empire. Foiled by the pursuing photographers, he flees into the ocean. During another visit to the detective, a package inscribed "MU" arrives for the Admiral. Contained within is a film depicting the thriving undersea continent (with its own geothermal "sun") and demanding that the surface world capitulate, and prevent Jinguji from completing his Atragon submarine, named Gotengo. The UN realizes that the Atragon may be the world's only defense and requests that Admiral Kosumi appeal to Jinguji. Concurrently, Makoto's stalker is arrested and discovered to be a naval officer under Jinguji. He agrees to lead the party to Jinguji's base but refuses to disclose its location. After several days of travel, the party find themselves on a tropical island inhabited only by Jinguji's forces and enclosing a vast underground dock. Eventually Captain Jinguji greets the visitors, though he is cold toward his daughter and infuriated by Kusumi's appeal. He built Gotengo, he explains, as a means to restore