Beautiful space alien princess Lum invades Earth on her UFO, and unlucky Ataru Moroboshi's world gets turned upside down! Will Lum become Earth's electrifying new leader? Or will Ataru somehow miraculously save Earth from space alien onslaught?

Inaba the Rabbit Man is trying to get a promotion, but to level up he has to pick a rare flower that only grows in space-time, and he needs to find a girl who will come with him on his dangerous quest! But when he asks Shinobu to accompany him, he gets Ataru and Lum in the bargain too! Is his promotion doomed? Later, some random dude shows up at Tomobiki High claiming to be Lum's fiancé! He whisks her away to be married on his darkness-draped home planet, and the only way Ataru can save her is by saying "I love you." When he can't bring himself to do it, Lum gives Ataru an ultimatum that balances the fate of the world against his heart! Is Earth doomed?!