The Galactic Emperor Zemu is conquering one planet after the other, planning to expand his empire to the known limits of the galaxy. The reason for his success are huge robots who fight in his armies, developed with the technology invented by the genius scientist Dr. Lulu. But the doctor understands herself that her inventions have caused misery and destruction to other nations. She runs away, taking design plans for the giant robots with her. She arrives on the Earth (Japan, to be exact) shortly after World War II, and with the help of local scientists, develops a powerful robot, that alone can protect Earth from Zemu's attacks: Super God Trooper Zeroigar!