The series takes place on an artificial celestial body known as Aposimz (アポシムズ, Aposhimuzu), which is 200,000 kilometers in diameter.

Five thousand years ago, people who lost a war against the inhabitants of the core were exiled to the surface, a cold and harsh environment.

Certain people have been transformed by special "codes" into Regular Frames (正規人形, Seiki Ningyō), beings composed of a substance called placenta (胞衣, ena) and fueled by Heigus Particles (ヘイグス粒子, Heigusu Ryūshi), which renders them biologically immortal and makes them stronger and more resilient than normal humans.

Regular Frames are also able to assume an armored form and each one has a unique special ability or weapon.

[7] Kodansha also started publishing a full-color edition of the series on November 8, 2019,[8][9] and five volumes have been released as of August 8, 2022.