Shiina and Akira are awkward, self-conscious teenagers, struggling with school and self-esteem whose lives change forever when they encounter and bond with small, cuddly extraterrestrial creatures, two of a menagerie of spaceborn entities now on Earth, including terrifying Shadow Dragons, flying beasts of vast and lethal powers. But Shiina and Akira are not the only ones with such unearthly familiars, and an underground network exists of such Earthling/alien mates but is their aim to protect the planet or destroy it?