The Shiranui Clan have planned for 2000 years to conquer Japan in retaliation for their nomadic ancestors being banished from the country by the Yamato Clan. Each armored ninja-like member of the clan controls a gigantic robot warrior in order to overthrow the "Yamato Government," as they call it. In response to this terrorist threat, Japan's National Security Organization send agent Gentaro Shizuka, disguised as what can best described as a Spaghetti Western version of a singing cowboy, to stop their plans with the assistance of comical, mountaineering-clad Goro Kirishima. In an unusual direction for such tokusatsu programs, it is not the heroic but often surprisingly ruthless Gentaro but the bumbling, bespectacled Goro who has the power to become the giant cybernetic superhero Iron King by touching the medals on the sides of his funny red Turning Hat and shouting "Iron Shock!" when danger threatens. However, often Iron King is unable to defeat the clan's giant robots without help from Gentaro, who wields a weapon called the Iron Belt that can become a slender rapier-like sword or an infinitely extendable metal whip capable of hurting giant monsters. In addition, transforming into the hydrogen oxide-powered Iron King quickly dehydrates Goro, and he can only remain as Iron King for a short period of time. Strangely, although Gentaro knows Iron King's time limit comes from using up his water supply he never manages to connect it with Goro's omnipresent thirst until the final episode. In the tenth episode the Shiranui Clan is destroyed but their place is taken by the skull-symboled keffiyeh-clad Phantom Militia who also use giant robots to enact their revolution against the Japanese government, although rather than being humanoid in shape theirs take the form of dinosaur-like kaiju. From the nineteenth episode to the end of the series Gentaro and Goro battle black cloak and Puritan hat-clad white-masked aliens called Titanians who have various inhuman powers such as flight, body-possessing mind control and the ability to enlarge themselves to giant size. Upon doing the latter they are then able to assume insect-like monster forms.
