1. LACRIMA:
The mysterious virtual universe that Mado and his classmates were injected into. Long ago, it used to be a single unified world protected by the Empire of Solheim, and blessed by the Astrals. But later on, a war waged, and Lacrima was divided by a sacred barrier into smaller planetoids harbored within two separate Realms. The Realm of Light is where the humans reside under the rule of the Axiom Government. And the Realm of Darkness which is the home of the cursed creatures, such as demons, goblins, ogres, etc..
2. PLANETOID:
A small planet that harbors people sharing the same culture and knowledge. Some planetoids are heavily technologically modernized, while others depends on magic and relics. Each planetoid is situated within a Level. The further away the planetoid is from the sacred barrier, the safer it is from demons infestation.
3. AXIOM:
The governing system that rules the Realm of Light. It's mainly managed by four main heads known as Administrators. One of these four is the chief leader of the army's legendary alpha squadron, the Eternal Knights.
4. Demons:
Mysterious vicious creatures originated from the Realm of Darkness. They appear to reek havoc across various planetoids in attempt to invade them, and destroy them completely. As Jaden goes from one planetoid to another, he encounters multiple types of demons. Some even seem to possess a sinister degree of intelligence.