The ancient Mu Empire, from under the seas, is launching an attack on the world above. They are trying to seize engineers and experts, which brings them to the attention of Japanese photographer Susumu (
Tadao Takashima) and retired Admiral Kusumi (
Ken Uehara). The agents of Mu also try to kidnap Kusumi and Makato (
Yoko Fujiyama), the daughter of the Admiral's former comrade Jinguji. Makato thinks her father was lost in the war but Mu seems to think he is alive and building a new super submarine...
Kusumi admits it is true and they go to find Jinguji, taking along in tow a reporter (Kenji Sahara) who is so overtly a Mu agent it is ridiculous! On a remote island in the Pacific they find Jinguji (Jun Tazaki) and he shows them the incredible flying submarine he has developed in secret. However, as Mu begins it's attacks on the world above and turns a big chunk of Tokyo into a crater... Jinguji won't help! He says his submarine is only for the glory of the Japanese empire! Can Kusumi and Makato persuade Jinguji to change his mind before the mighty forces of Mu led by the Empress (Tetsuko Kobayashi) conquers the world?
Very good Japanese sci-fi / monster nonsense (Mu has a living god sea serpent though it is beaten rather easily). The film drags at times and some of the storyline doesn't make a lot of sense but this is a fun film overall full of terrific special effects and mayhem. Jinguji's tension, torn between duty and his love for his daughter adds a welcome bit of depth to the film.