APOSIMZ, Volume 9

There's a distinct visual element to APOSIMZ that sets it apart from many other manga, a lightly-inked, barely-shaded style that lends it a dreamlike quality. - Anime News Network

The artificial celestial body Aposimz measures 120,000 km in diameter.
Most of its volume is its core space, which is covered by a superstructural shell.
Fifty centuries ago, the people who lost the war against the core lost their right to reside legitimately on Aposimz, and were stranded on the frigid surface. hey face rampant Frame Disease and aggressive automatons which appear frequently on the Ruins Level.

Yet even so, somehow the people survive.