Industrial espionage gets in the way of love and marriage for factory worker Katayanagi.

Up until this point, young Sayuri Nanjo has had to live most of her life in a nun-run boarding school for orphans and away from her parents. That's all about to change when her real father mysteriously comes to get her and finally bring her home.

Two young boys sneak aboard a spaceship and find themselves whisked away to the mysterious planet Terra. There, they encounter Gamera's old foe Gyaos and two female aliens with a taste for human brains. Gamera must save the children and battle the new monster Guiron, whose entire body is a deadly living weapon.

A decapitation at the hands of the shogun's monstrous misbegotten son kicks off the action and draws nomadic Nemuri Kyoshiro (Raizô Ichikawa) into more sword-fighting adventures when he's blamed for the beheading. Meanwhile, the head-chopper's mother is busy knocking off the shogun's lawful heirs to secure the shogunate for her son.