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?

Lum, Ataru, and Shinobu accidentally get their hands on a key of fate that unlocks the door to their future! Well, a future. Shocked by the terrible destiny in store for them, the friends do their best to find their happily ever after. But why is every new version worse than the last?! Later, boy-phobic Asuka can finally breathe a sigh of relief when she begins attending an all-girls school with such tight anti-boy security that even gentleman dogs can't wander on campus. Her paradise is soon compromised, however, when the Tomobiki High principal comes up with a creative intramural challenge that shatters the peace of Fastidious Female Junior High!