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!

An animated pilot film for Ninja Bugei-chou released to the public over three decades later on Ninpuu Kamui Gaiden DVD volume 7. The pilot film was created in 1969 as director Nagisa Ooshima was wanting to make a TV animation to build off his controversial film from 1967. The pilot was rejected by Shirato himself (the original comic creator the film was based on) and the plan was changed to animate Ninpuu Kamui Gaiden instead, a side story to the Kamui Den manga also created by Shirato. Though with this change, Ooshima did not partake in Ninpuu Kamui Gaiden's production.

Based on the novel trilogy of the same name by MAYUMURA Taku (眉村 卓), Time Stranger is the story of a bunch of teenagers getting transported back in time through Japan's history, and getting mixed up with samurai shenanigans.