History Manga / WelcomeToDemonSchoolIrumaKun

* AbsurdlyPowerfulStudentCouncil: {{Subverted}}. They do have a lot of influence among the faculty, which is how Iruma was able to get permission slips from several teachers, however they are also still seen as another student group and are subjected to the same rules as them.

* ExtranormalInstitute: Babyls is a school for Demons. Besides the student body it actually acts like a normal school.

* GreaterNeedThanMine: Kerori's friendship with Iruma truly starts when he does this for her. During one concert, Iruma wins the chance to meet Kerori's stage persona Kuromu between shows. There Iruma confesses admiration for her as she handles being in the spotlight so well as he wants to stay in the background and unnoticed. This angers Kerori as she realizes all the fame-grabbing things that supplanted her own news were unintended as such and causes her to black out from using too musch of her ice magic. Iruma recognizes his own part in overexerting her and with Azz and Clara's help, they take the stage as female dem-dols as an opening act so Kerori has time to recover. Kerori is shocked at this self-admitted boy who wants to stay in the background is going against that desire to help her. Now that she is recovered, she joins her classmates on stage to the delight of her fans.

* GreaterNeedThanMine: Kerori's friendship with Iruma truly starts when he does this for her. During one concert, Iruma is wins the chance to meet Kerori's stage persona Kuromu between shows. There Iruma confesses admiration for her as she handles being in the spotlight so well as he wants to stay in the background and unnoticed. This angers Kerori as she realizes all the fame-grabbing things that supplanted her own news were unintended as such and causes her to blackout. Iruma recognizes his own part in over exherting her and with Jazz and Clara's help, they take the stage as female dem-dols as an opening act so Kerori has time to recover. Kerori is shocked at this self-admitted boy who wants to stay in the background is going against that desire to help her. Now that she is recovered, she joins her classmates on stage to the delight of her fans.

* HoistByHisOwnPetard: Kalego, as a familiar, demands Iruma to undo the summoning. Robin stops him from doing so by citing the school guidelines "be dignified and never allow specific exemptions". The person who wrote said guideline was Kalego himself.
* HoldTheLine:

* {{Guyliner}}: All of the men of the Demon Realm seem to paint their nails with black nail polish (as do the women). Iruma begins to do this as well during the Music Festival arc after he chips his nail while practicing piano and one of his classmates recommends it, with it being revealed there that the polish is made of a stabilizing agent to stave off the nail-cracking problems that come from overworking a person's fingers, providing a sensible reason for both girls and guys using it.

An anime adaptation produced by Creator/BandaiNamcoPictures and directed by Makoto Moriwaki [[note]] of ''Anime/OruchubanEbichu'', ''Anime/OnegaiMyMelody'', ''Anime/TanteiOperaMilkyHolmes'', ''Anime/JewelpetKiraDeco'' and ''VideoGame/{{PriPara}}'' fame [[/note]] began airing on October 5, 2019, the first season of which ran for 23 episodes. A second season began airing on April 17, 2021 and ran for 21 episodes. A third season began in October 2022 with a total of 21 episodes. A fourth season has been confirmed to be in development and is slated to start airing in April 2024.

* BetterOffWithTheBadGuys: The story starts with fourteen year-old Iruma being sold to the devil by his own deadbeat parents and brought to Hell. Fortunately, all said devil wants is a grandson to show off to his friends and Iruma starts to live a life of luxury. He stops trying to go back to the human world when he remembers how his parents stole anything he produced and made him live in the wilderness.

** When Iruma is first visiting the Magical Apparatus Battler, Kirio shows him some some paper dolls which can move when infused with magic, but even moving it slightly causes Kirio to vomit up blood. During the sleepover during their preparation for the Battler Party, Clara is seen playing with them. [[spoiler:During Kirio's attack on the school, Clara uses her duplication techniques to create hundreds of them and Asmodeus empowers them, letting them find the pathway for Iruma to bypass the barriers and find Kirio's secret room once more]].

* ElectiveMonarchy: The Thirteen Crowns and the Three Greats are the current leaders of the Demon World, but none of them are the King. The next Demon King is to be selected by these two groups. It is believed one of their members in either group is likely to become the next Demon King. [[spoiler:However, by chapter 200, the Greats have come to the conclusion neither any member of the Thirteen nor each other should be the next Demon King. Selecting any of them would create in-fighting and destabilize the Demon World further. Instead, they have chosen to nominate one of their own grandsons for title of Demon King and have asked the Thirteen Crowns to help evaluate and mold these candidates into a proper King all could follow. They will even allow the Thirteen to nominate candidates of their own]].

* EvilMakesYouUgly: What happens when demons have succumb to their Wicked Phases for too long and returned to Origins. They truly become demonic and evil, and become a lot more dangerous. This helped clue Azz in when he encounters [[spoiler:Amy]] who has the same eyes as the Origins demons.

** The ending for Season 2 is in constant flux, with most of the silhouetted visuals staying the same, but the full-color reveals of the silhouettes changing. In the shot of Ameri being read to by Iruma, Ameri eventually gets replaced by Goemon. Later, the girls in their theme park attire is replaced by the silhouetted version being printed out as a photo, with the reading shot being replaced by Ameri grabbing the photo... and then she is later replaced by Allocer in ''that'' shot. Keroli is initially in both the opening and ending group shots, but later appears as Kuromu in the ending group. Kuromu in mid-performance is later replaced by Sabnock and Asmodeus singing together.

** When Iruma was made to give a speech on opening day, Sullivan gave him one with a note saying this is so he won't "trip and fall on you're first day". After reading it one of the teachers tells him it was a forbidden spell that if said incorrectly would have blown him apart, but since he said it correctly it will prevent him from tripping or falling for the entire day.
** Kalego's conditions for the Misfit Class to move into the Royal One states they must get signed permission from every faculty member. [[spoiler:Iruma and the class initially think this just means the teachers, but Kalego is referring to the gardeners, janitors, librarians, food services, school store employees, and so on, as well. Thankfully the rest of the staff, impressed by Iruma's ongoing kindness to them, shows up with the slips without being asked]].

* SpellMyNameWithAnS:
** The name of the [[Franchise/HarryPotter Hogwarts]] {{Expy}} that Iruma and co. attend could be read as "Babyls", "Babirus", "Babyrus" and "Babylus". The anime for the most part goes with the first one, while the manga uses them interchangeably depending on who's translating that day.
** The name demons give to clubs can be translated as Battra, Battler, and Batora. Like with the school name, the anime mostly sticks with the first one, while the manga uses whatever the current translator of the chapter decided to translate it as.

** Henry Azazel, eager for his daughter to gain some working experience and avoid time with Iruma, asks she join the security team for the Evidol Games. When she goes to check out a complaint of a commotion in one room [[spoiler:it's Iruma's room where he and his team are getting ready for the competition and they need a fourth demon for their team and whom they can trust]].

* When the Thirteen Crowns are first shown on screen, only twelve are seen or mentioned. [[spoiler:This discrepency in numbers is later expanded as there is one missing seat reserved for Derkila and his request they protect his empty throne]].

* ''Welcome to Demon School! Iruma-kun if: Episode of Mafia'' (魔入りました！入間くん if: Episode of 魔フィア; Mairimashita! Iruma-kun if: Episode of Mafia): An AlternateContinuity that began serialization in September 12 by Hiro and original concept by Osamu Nishi. As the title suggest, it's about Iruma who becomes part of the Mafia by helping [[TheDon Don Sullivan]], who adopts and raises him to be the successor of the Babyls Crime Family.

* ''Welcome to Demon School! Iruma-kun if: Episode of Mafia'' (魔入りました！入間くん if: Episode of 魔フィア; Mairimashita! Iruma-kun if: Episode of Mafia): An AlternateContinuity that began serialization in September 12 by Osamu Nishi. As the title suggest, it's about Iruma who becomes part of the Mafia by helping [[TheDon Don Sullivan]], who adopts and raises him to be the successor of the Babyls Crime Family.

* ThirteenIsUnlucky:

** The time it takes for a summon contract to be cancelled is 13 hours, and since Kalego very much wants to stop being Iruma's familiar, he spends the entire time following the one-year waiting period closely watching the boy in case somebody tries to trick him into using a summoning circle, which could be considered Iruma's unluckiest day in the demon world.

** Kalego's conditions for the Misfit Class to move into the Royal One states they must get signed permission from every faculty member. [[spoiler:Iruma and the class initially think this just means the teachers, but Kalego is referring to the gardeners, janitors, librarians, food services, school store employees, and so on, as well. Thankfully the rest of the staff, impressed by Iruma's kindness to them, shows up with the slips without being asked]].

* TheDreaded: Bachiko Barbatos describes the Barbatos clan archers as the Dreaded to many other demons. With their ability to hit any target, even one fleeing away. She further adds how if this done when the victim is unsuspecting and the archer times it right, then a single shot from an archer can turn the whole battle. This is why when others speak of the Barbatos clan the word that comes up most frequently is "despair."

** The Spectral Violet means "If I lose you, I bid the world farwell."

** Creator/KayliMills previously played a character who [[Literature/KonoSuba wanted friends but fails spectacularly as she gets bullied by her "rival/best friend"]]. Here, her character Clara gained 2 at the start and that was an improvement.

** Despite Iruma finding out the Cannon Ball Execution game was just Dodgeball, it's still played by demons who have enough strength to make the game quite lethal to a frail human.

** In chapter 142, [[spoiler:Baal, Kiriwo, and Ocho learn that he's a human from a bug planted on his clothes]].
** In chapter 146, [[spoiler:Sullivan and Opera tell Bachiko that Iruma's a human]].
** In Chapter 184 [[spoiler: Kerori reveals to Lied that she and Iruma are Kuromu and Irumi.]]