APOSIMZ (Celestial Body)

* Japanese
* English

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.
They face rampant Frame Disease and aggressive automatons which appear frequently on the Ruins level.
Yet even so, somehow the people survive.
 -Volume 1 Chapter 1, Pages 2-3

**APOSIMZ** is an enormous artificial planet that serves as the main setting of *Aposimz*. The human inhabitants of APOSIMZ dwell in both its Surface, which is a vast icy wasteland, and inside its much more idyllic Core. Between those two layers are the derelict mechanisms of the Ruins and an impenetrable Megastructure shell. It is said that five thousand years ago, a war between nations in the Core ended with the losing side being expelled to the inhospitable Surface. While some still dream of returning to the Core one day, most people are focused simply on the struggle to survive the Surface's many dangers.

## History

*This section contains major spoilers revealed in Volume 9.*

The precise origins of APOSIMZ are unknown, but the origins of the schism between the people of the Surface and the people of the Core are explained by Titania.

The Core of APOSIMZ is not hollow, but a mass of placenta containing a virtual world and the digitized personalities of every human who ever inhabited it. When humans who live on the Surface die, their personalities are captured and they are reconstituted within the Core to live on as immortal, virtual beings. APOSIMZ itself is a massive mechanism to support this simulation, all for the sake of perpetuating the human race and ensuring its inhabitants' eternal comfort and happiness. Titania is the construct responsible for maintaining APOSIMZ and carrying out its primary purpose.

Five thousand years ago, a faction of Core dwellers asked to be given physical bodies and allowed to take up residence on the Surface, even though it was never designed for human habitation. Titania, programmed to keep humans happy, complied with their request, but promptly ceased to recognize the new Surface dwellers as her wards because the Surface had no relevance to maintaining the Core.

Centuries passed, and the Surface people adapted to their harsh environment and forgot the truth of their circumstances. They came to believe that their ancestors had been exiled from the Core to live on the barren Surface after losing a war, that it was an ancient injustice. They tried to demand of Titania that she open a gateway from the Surface to the Core so that they could return, but Titania continued to ignore them. When the Surface people began burrowing down to the Core themselves, damaging APOSIMZ, Titania classified them as a threat to APOSIMZ. She decided to exterminate them since their population had become too large to reintegrate into the Core without greatly disrupting the lives of the existing Core dwellers, which would violate her directives.

Titania delayed her purge as the Surface people became distracted and weakened by wars among themselves and the spread of the Frame Disease. Unexpectedly, the Surface people created a new Code that bestowed the ability to see the future, which Titania saw as a tool that could enhance the security of APOSIMZ. Consequently, she reclassified them as beneficial to APOSIMZ, which meant she could welcome them into the Core. All she needed was to find someone who was compatible with the Code to bear it and become the guardian of APOSIMZ, and Nichiko Suou fulfilled that role. Unfortunately, the ability to see the future changed Nichikou, causing him to take actions to pursue his own goals that also endangered APOSIMZ. To avoid having to kill the Surface people to protect APOSIMZ, Titania chose a new guardian to eliminate Nichikou: Etherow.

## Geography

* Surface
	+ Northern Composite Slab
	+ Southern Composite Slab
* Ruins
* Megastructure
* Core

## Countries

* Rebedoa Empire
* White Diamond Beam

## Trivia

* APOSIMZ's diameter of 120,000 km makes it almost twice the size of the gas giant Jupiter, which has a diameter of 69,911 km.
* The manga *Knights of Sidonia*, another of Tsutomu Nihei's works, briefly mentions a starship named Aposimz that left the Solar System in the 24th century, one of hundreds of Seed Ships launched from Earth before it was destroyed by the Gauna. While *Aposimz* and *Knights of Sidonia* are not officially confirmed to be set in the same universe, it is possible that the artificial planet APOSIMZ is a future version of the Seed Ship Aposimz, as the purpose of both was to preserve humanity.