In the Andromeda galaxy there's a planet of a highly developed human civilisation. The gentle Prince Itaka and another kingdom's beautiful Princess Lilia are about to enter a love-marriage and take over the throne, when they discover a strange object on the nightsky. Later it lands on the planet, and an alien, mechanic civilization invades King Itaka's peaceful country making nearly everybody their slave. On a fateful night Queen Lilia gives birth to twins, and to avoid misfortune, the nanny Tarama takes one of the babies away, and entrusts it to the gladiator Balga. They still don't know, that the children were born with strong powers, and hold the key to the fight against the enemy that's searching to destroy every human civilisation on the planet...

The film is an adaptation of a story in Chinese mythology (in particular, the epic fantasy novel Fengshen Bang) about the warrior deity Nezha. After a gestation period of 3.5 years, Lady Yin, the wife of General Li Jing, gives birth to a flesh ball, which becomes a lotus flower, from which Nezha is born. Nezha is born able to walk and talk, and is taken on as a student of the immortal Taiyi Zhenren. The Dragon Kings of the Four Seas, tired of being peaceful, have become cruel and destructive, plaguing China with destructive storms and a drought. The people beg for rain, but the East Sea Dragon King Ao Guang ignores them, telling the yaksha Ye Sha to go and find children for him to eat. Ye Sha captures one of Nezha's friends as he is bathing by the ocean, and Nezha confronts him, injuring him badly. Ao Guang sends his third son, Ao Bing, next. Ao Bing is killed by Nezha, infuriating Ao Guang. A variety of confrontations ensue between Nezha and Ao Guang. Ao Guang and the other Dragon Kings wreak havoc on the people, causing storms, floods and all manners of natural disasters. Seeing this, Nezha takes his father's sword, tells his parents that he is returning their flesh and bones to them, and calls out for his master before committing suicide by slitting his throat. He is reborn with the help of his master, again from a lotus blossom, and is given new weapons and abilities. After breaking into Ao Guang's underwater palace, he confronts Ao Guang and the other Dragon Kings again, and is finally triumphant.

Dr. Tatsunoko of Tatsunoko Research Center goes undersea accompanied by his daughter Asari to inquire into some mysterious radiation and discovers there a giant shell and it is known that the radiation comes from a globe laid inside the shell. Then Asari finds an object in the shape of compact with a message in it. It says that a space alien from the Planet of Parlum which is on the verge of extinction is lying in the globe. Suddenly a boy with a strange look appears out of the globe and goes wild. He is the very person mentioned in the message with the name of Ace. His source of energy for superhuman power is what is called space food and he can fly with the help of Silver Ring made with energy collected instantly in the aerial environment. Also he is able to use it as a weapon to fight the enemy with. Supported by his friends including Asari, Ibo the robot dog, and Hermit Crab Reporter, he gallantly goes into action to settle various difficulties caused by mystic robots and brutal space invaders.

October 1941, as the second World War threatens to destroy the civilized world, an unforeseen complication suddenly occurs. An alien invasion! Despite the sudden appearance of these extraterrestrial aggressors, the Axis and Allies continue their destructive conflict. Only the Kishin Corps and their giant Geo-Armor Robots (a.k.a.: Kishin), developed from a captured alien robot soldier, stand between the Earth and total annihilation! A teenager, named Taishi, suddenly finds himself at the center of a struggle over a mysterious black attaché case entrusted to him by his father, Professor Tokamura. The case contains the controlling mechanism for one of the giant Geo-Armor Robots, and the Japanese Kanto Army, the alien invaders, and the Kishin Corps all want to recover the device! Between the spies, the armies, the aliens, and the Giant Robots, Taishi is in for an epic adventure—if he can survive it!