Mazinger Z vs. Devilman is a 1973 animated movie that crossed over two then-popular Anime series, both of which were created by Manga artist Go Nagai. While fighting with some of his enemies Mazinger Z inadvertently knocks them into a volcano, where they crash into the prison of the Satan race and release Phoenix Jenny! Dr. Hell, learning of this, frees the rest of the Satan race and teams up with them to defeat Mazinger Z, and their ability to fly proves to be too much for our hero. Meanwhile, Devilman is also individually fighting the members of the Satan race, but their combined power is too much for him as well; can Mazinger and Devilman put aside their differences and team up to defeat Dr. Hell and the Satan race?

For the past 150 years, humanity’s two greatest nations have been deadlocked in a meaningless war. In what is hoped to be a miraculous victory, the Alliance embarks on a battle to break through the Empire’s frontline. Like many other “decisive” battles, this can only end in disaster; a sentiment shared by Imperial nobleman Reinhard von Lohengramm and Alliance Commodore Yang Wen Li, both of whom realize how to turn the fight in their favor. And while the tides of war may never change, these two men must rise to the occasion, solidifying their place in history as heroes.

To help him with his summer vacation project, Doraemon gives Nobita a kit which allows him to create a new world. The duo and their friends then go on a journey to witness the evolution of life.