In the Netherworld, humans are viewed similarly to fairies or Santa Claus in the human world—they are believed not to exist. Some high-ranking demons are told that humans do exist.

Bloodline Abilities can only be used by members of that specific family. For example, the Valac family (Clara's family) bloodline ability cannot be used by the Asmodeus family (Alice's family) or Iruma.

Familiars are not constantly summoned. After the initial summoning and contract, they must be summoned individually each time using a summoning seal or similar method.

The Abnormal Class (Misfit Class) is the class Iruma, Alice, and Clara belong to. It consists of students who caused trouble at the start of enrollment, but they aren't necessarily "delinquents" (like picking fights or skipping class constantly).

The ranks of the faculty are not public knowledge, with the only note being that "Kalego and Balam are the only ones at Rank 8 (Cheth)." Other teachers are likely Rank 7 (Zayin). It is extremely unlikely for students to know the faculty's ranks.

About Ranks: 1 (Aleph): Minimum rank at enrollment 2 (Bet): General student level 3 (Gimel): Quite impressive 4 (Daleth): Minimum rank required for graduation 5 (He): Average level of graduates 6 (Vav): Impressive 7 (Zayin): Most Babyls teachers are at this rank 8 (Cheth): Very impressive 9 (Teth): Incredible 10 (Yod): The Demon King is chosen from this rank

Ranks can be raised through rank promotion exams during the school year (such as Execution Cannonball or the Harvest Festival). From Rank 6 onwards, ranks cannot be raised through school exams and must be earned through an exam by the 13 Crowns called Scala. The passing rate for Scala is approximately 6%.

Furthermore, the members of the 13 Crowns are as follows:

Demon King: Derkila (Known as the Demon King of Disappearance)

The Three Greats: Sullivan (Iruma's grandfather. No blood relation. Usually has a mild-mannered and cheerful personality. An extreme doting grandfather. Chairperson of Babyls Demon School.)

The Three Greats: Belial (Has a grandson named Berry Raspberry Belial. Usually has a friendly but suspicious, boisterous personality. An extreme doting grandfather. President of the Underground Academy Jackapo.)

The Three Greats: Levi Lady (Has a grandson named Raz Levia. Usually beats up anyone who calls her an "old lady trying to look young," and has a powerful, boisterous personality. An extreme doting grandmother. President of the Demon Sea Academy Levia-ron.)

Heroic Second: Beelzebuth (A hard worker.)

Heavenly Eye: Astaroh

Gluttony Lord: Behemolt (Eats a lot. Removed when deciding the New 13 Crowns due to being missing.)

Head of the Four Corners: Amaimon

Spirit Master: Paimon (Has a heavy regional accent.)

Chief of Demon Border Control: Henri Azazel (Father of Ameri Azazel, the Student Council President of Babyls. Usually has a calm, strict personality and is loyal to his duties. Somewhat of a doting parent. His bloodline ability is Romanticist, a self-suggestion magic that enhances all abilities. Current head of the Azazel family.)

Lord of Seduction: Amaryllis Asmodeus (Mother of Alice Asmodeus. Usually has a glamorous and innocent personality. Quite a doting parent. Current head of the Asmodeus family.)

Dark Emperor: Glasya (Has never appeared in the story. Like Behemolt, removed when deciding the New 13 Crowns due to being missing.)

Thunder Lord: Baal (Uncle of Iruma's classmate, Sabro Sabnock. A junior among the 13 Crowns, but always maintains an irreverent attitude and has the courage to voice opinions to superiors without fear. Behind the scenes, he is the mastermind aiming for the collapse of the Netherworld's order to return it to its former chaotic state, commanding a criminal group called the Six Fingers, said to be involved in all manner of evil.)

New 13 Crowns (Shortly after Iruma enters his second year):

No changes except for the removal of Demon King Derkila, Gluttony Lord Behemolt, and Dark Emperor Glasya. The new members are as follows:

Out-of-the-Box Lord: Mephisto (Usually has a friendly and playful personality. Known as the "Kingmaker" for leading the former Demon King to the throne. He wants to make someone "protagonist-like" the Demon King, and introduces himself to such people as "Mephisto Pheles.")

Top Archer: Bachiko Barbatos (Has Iruma as her archery apprentice, and Robin Bars, a teacher at Babyls, as a younger cousin from a branch family. She has a foul mouth and a strong-willed personality, but is a compassionate and caring "big sister" type. Her bloodline ability is 100-Shot 100-Hit, which allows her to form a bow with her own mana and fire a hundred shots a day that can pass through obstacles like walls and always hit the target. Current head of the Barbatos family. It seems the family has a Grand Head and a Head.)

Dog Emperor: Narnia Naberius (Older brother of Kalego Naberius. Has a cold, strict, and serious personality.)