In the mid-21st century, mankind has begun 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 born in space and still alive. But survival itself is no longer guaranteed - a military satellite triggers a disaster during an operation to capture Halley's Comet, and Ushiwaka and his fellow colonists must find a way to survive when both their country and their company abandon them. Can they escape before the nuclear reactor on the asteroid melts down? Or are they doomed to die as they lived, among the stars?