*Aposimz is an artificial celestial body 120,000 kilometers in diameter. Most of its volume is an underground space enclosed by a megastructure shell.

Fifty centuries ago, those who lost the war waged in the core lost their right to reside in Aposimz and were left on the freezing surface. The Frame Disease spreads. Aggressive automatons frequently appear in the ruins. Yet, people managed to survive somehow.

While on a training march, Etherow, Biko, and their companions from the settlement 'White Diamond Beam' rescue a mysterious girl being pursued by soldiers of the Rebedoa Empire. The 'Code' and seven 'Bullets' she entrusts to them are items that could drastically change the fate of the world—!*

One day, the Empire invaded, destroying White Diamond Beam and killing its people. Only Etherow survived by being reincarnated with a Code by Titania. During his journey, he meets Keisha, and the two begin their adventure with a plan to kill the Emperor of the Empire.