Although it has never been released in Japan, Kamen Rider fans in Japan refer to it unofficially as Hanuman and the 5 Kamen Riders (ハヌマーンと5人の仮面ライダー,Hanumān to Gonin no Kamen Raidā?).
The film teams five Kamen Riders (1, 2, V3, Riderman and X) with the Hindu god Hanuman (fresh from his appearance in The 6 Ultra Brothers vs. the Monster Army) against X's adversary King Dark (who appears in his regular giant moving statue form, and alternately in a human-sized form), who drinks the fresh blood of young women. He captures a scientist and his girlfriend, and threatens to drain her of her blood unless he use his technology to create an army of mutant animal men to confront the five Riders.
Unlike Chaiyo's two official co-productions with Tsuburaya Productions in 1974 (namely The 6 Ultra Brothers Vs. the Monster Army, The 11 Ultramans vs. The Monster Army and Jumborg Ace & Giant), this production was unauthorized by Toei Company, Ltd., which produced the Kamen Rider shows. Chaiyo had initially approached Toei, who turned down their plans for producing their own Kamen Rider movie.