This world consists of three layers: the bottom layer, the Deep Demon Realm; the top layer, the Human Realm; and the middle layer, the Coexistence Realm, where humans and monsters live together. You are the ruler of the Coexistence Realm—a Demon Lord despite being human. Though you are the strongest Demon Lord capable of mastering all forms of magic, you have no desire for world domination. Instead, you live peacefully with your retainers, spending your days leisurely while working toward a future where monsters and humans coexist. Meanwhile, the Great Demon Lord of the Deep Demon Realm and the King of the Human Realm believe you are a threat to the world. Driven by a desire to eliminate you, they constantly send soldiers and heroes your way. Good luck, you'll need it!

About the World⬇

The terrain is shaped like a greatsword, hence the name Gladius. Gladius has three layers: the top layer is the Human Realm, Elef; the middle layer is the Coexistence Realm, Genesis; and the bottom layer is the Deep Demon Realm, Diaros. In Gladius, the sun rises and the moon sets equally across all layers. The mana required for magic becomes denser in the lower layers, so the Deep Demon Realm is home to many powerful monsters. On the other hand, the Human Realm is closest to the heavens, where the voice of God is heard most clearly, making it easy to receive blessings. The middle layer is the most balanced, having an environment similar to Earth but infused with mana. Each layer contains various large and small countries, villages, and towns. The largest countries are located in the center. Furthermore, because each has its own culture and ideology, wars sometimes break out. To travel between layers, there are four springs located at the cardinal directions (North, South, East, West). Jumping into one allows you to travel to the desired layer. These four springs exist identically across all three layers. In other words, if you dive into the Northern Spring in the Human Realm, you can emerge from the Northern Spring of any other layer. Since the capital of each realm is centrally located, the distance is the same regardless of which spring you use.

About the Human Realm, Elef A world that developed through divine blessings. Thanks to these blessings, there are no storms, and crops grow year-round. It is like a world of eternal spring. They loathe the demon race and will kill them on sight to use their parts as materials for tools. Even though mana is thin, it drifts in the air, so they have no trouble using magic. The King of Elef believes their world is the only righteous one and wishes to rule the lower layers. In addition to humans, angels and beastmen inhabit this realm, but they are constantly fighting over land.

About the Coexistence Realm, Genesis A world with four seasons where mana and blessings are most stable. Because it accepts humans and demons equally, it has the richest ecosystem of all layers. Humans and demons cooperate on everything from infrastructure to entertainment to build a better nation. Sirens inhabit the only sea bordering Genesis. It has the most developed culture.

About the Deep Demon Realm, Diaros A lawless world with the densest mana. All kinds of demons exist in this layer. Strength is everything, and they despise humans as weaklings. It is as cold as being deep inside a cave, and mana crystals grow everywhere. Monsters grow stronger by eating these crystals. Monsters that consume a lot of mana accumulate it in their bodies, making them targets for others. The King of Diaros believes their world is the only righteous one and wishes to rule the upper layers.

Note: Regarding the Demon Lord Both the middle and bottom layers are considered demon realms. Therefore, the ruler of the Coexistence Realm is defined as the Demon Lord, and the ruler of the Deep Demon Realm is defined as the Great Demon Lord.