Every night is a championship race on the turbo-charged streets of Los Angeles. Dominic and Johnny are rivals who are the boldest, the baddest, the best, and turn their challengers into dust. Along comes a challenger. Dominic and Johnny know that he is tough and fast, what they don't know is that he is a speed demon detective trying to bust up a theft ring.

Lee Reyes plays Hiro, Master Tetsu's (Pat Morita)'s grandnephew, who is the last of the true ninja. His granduncle sends him to apprentice under Joe Kastle, (David Bradley), who is the American Ninja, to gain experience. Hiro cares only for his Game Gear and has little interest in the ways of the ninja. Joe in addition to being the American Ninja also owns a boat. In order to meet the American Ninja, Lisa (Anne Dupont) "varnishes" his boat when in fact she was asked to "tarnish" it. While having dinner Lisa is kidnapped by Viper (James Lew) and a host of multi-colored ninjas, and so the American Ninja and Hiro sneak onto a plane to Venezuela to save her. It is revealed that Lisa is the daughter of a scientist, under the employ of Glock (Clement von Franckenstein), who is being forced to develop a nerve gas for a Latin American despot. Ninja fighting ensues. Before the American Ninja and Hiro can rescue Lisa and her father from "Viper", the mysterious ninja that appears and reappears with a puff of smoke, the American Ninja must reawaken the ancient ninja tradition within Hiro with a 5 minute training montage. Viper is defeated in a climactic airplane battle scene, and Joe returns to Los Angeles to kiss Lisa on the bow of his boat.