Jet originally helped Captain Blue achieve his initial level of fame by acting as a cinematographer, and allowing the films to be shown in his theater. During his work, he met the actress Junko, and the two were soon wed and had their first child, Joe. He wanted to show his son a true hero. After finding Black Film, a cursed piece of celluloid, his wife Junko died in a car accident after giving birth to Jasmine. Jet's ideals were by then twisted into something else entirely. Jet found himself obsessed with finding the seven Rainbow Oscars, which would allow him to control the fate of Movieland, but more importantly, would make him the ultimate hero for his son. In Viewtiful Joe 2, he obtains a Black V-watch, and forms Gedow as the Dark Emperor to attack Movieland after King Blue's defeat. Joe and Silvia eventually beat him, and Jet reverts back to normal.
Jet's Henshin costume is a modified Samurai-style armor, with a crescent on the helmet and all black. In the final battle, he changes his costume to all-white instead. The colors associated with Jet seem to be black and white.
In the anime, Jet assists Joe, Silvia, and Junior as in the game, but the rainbow oscars are not present. Instead, the Black Emperor simply attempts to take over Movieland by spreading darkness and turning movies into "black films", films without happy endings. In the anime, however, he is controlled by an evil malevolence of darkness that Captain Blue was also manipulated by, the Evil King, whose diabolical goals were to take over the real world and control humanity's dreams. Jet ultimately turns back into his old self, but the Evil King then spreads his influence across reality, having broken out of Movieland. Joe is forced to confront his final enemy head-on through the power of a "white film," a piece of film with Captain Blue in a heroic pose. He uses its power to add the strength of the dreams of the people he met on his journey towards becoming a hero and destroys the Evil King at the end of the series. This might be the very enemy mentioned by Jet at the end of Viewtiful Joe 2.
He has a cameo in Viewtiful Joe's ending in Marvel vs. Capcom 3: Fate of Two Worlds.