In the mid-21st century, mankind has begun the exploration of space, and one company, Planet Catcher Corporation, has pioneered capturing asteroids and comets to mine the resources within them for use on Earth. On one such asteroid, Tortatis, lives 12-year-old Nanbu Ushiwaka - the only child ever to be born in space and survive.

In the mid-21st century, mankind has begun the exploration of space, and one company, Planet Catcher Corporation, has pioneered capturing asteroids and comets to mine the resources within them for use on Earth. On one such asteroid, Tortatis, lives 12-year-old Nanbu Ushiwaka - the only child ever to be born in space and survive.