Earth is being invaded by a race of unclean beasts who wish to take over the planet. However, since Earth's environment is hostile to the demons they hatch a plan to impregnate as many human females as possible in order to create a race of human/demon hybrids which will rule the Earth by proxy. But the "Interplanetary Mutual Observation Agency" sends a duo of enforcers to Earth to hunt down and destroy the alien race they call the ‘demon beasts’.

Youjuu Kyoushitsu Gakuen was published in English as Demon Beast Invasion by Central Park Media from December 1, 2002 to April 1, 2003.