During Iruma's entrance ceremony when Sullivan tricks him into saying that forbidden spell, why do all the teachers just stand there and let him risk his life when a single mispronunciation can lead to grievous harm? Because if they stopped him mid-chant, they would have certainly caused that mispronunciation and injured him.
In a case of Fridge Sadness, it's sad but makes sense when you realize the reason Iruma probably never told anyone in the Netherworld his birthday before being asked directly by Balam is because he's never had it celebrated before. Considering how awful his parents are and how accustomed he is to a life of only struggle, it's difficult to imagine he's ever been so much as wished a happy birthday. Let alone given any sort of proper party.
The fact that Ronove gets physically ill when touched by a man but is fine dragging Nafra around all day is an early hint that Nafra is actually a girl.
The Heartbreaker Competition isn't just for the Misfit Class' education and knocking them down from their dangerous pride. The teachers selected 26 fledgling demons who likely share similar arcs and potential to be great demons themselvesnote Zeze is able to do high-tier magic, Silvia and Chima are siblings of current Misfits, Fuwatoro is related distantly to Professor Stolas in order to teach them this lesson as well about keeping one's pride in check. Further, all the students watching get to see the teachers cut loose in ways they rarely do and impress on the students not to get too cocky either.
Later chapters of the manga indicate that both Azz and Clara are starting to make efforts to try and curb Iruma's absurdly incessant eating, with Clara even making a couple of mentions that Iruma seems to be putting on weight (which is often met with surprise and even a hint of indignation by Iruma himself). By Iruma's own admission, he eats constantly because of ingrained habit; he used to never know where his next meal came from, so he would eat whatever he could whenever he could, and was always running around either doing work or just trying to survive so he'd always work it off. Even though there's still plenty of danger for Iruma in the Demon World, this is likely the first time in Iruma's life that he's had access to a consistent and unrestricted access to food. So it stands to reason that this is the first time in his life Iruma would have ever been capable of eating enough that he could gain weight.
Considering how short Iruma is, one wonders if his parents worked and neglected him to the point of not mere starvation but malnutrition and his growth was stunted. This could've gone as far as him getting rickets. It really speaks volumes about how evil Iruma's parents were that they didn't even care for his physical health.
There is evidence of this with both how much taller his parents are and in his one year at school, he gets taller and his weight is in a healthy range for his age.
Iruma's parents were willing to sell their child just for some cash. While ultimately things worked out well for Iruma and he got to live with Sullivan, they were happy to trade him to a literal demon, not caring about his actual character or whether that demon would care for Iruma. What if a human trafficking ring offered to buy Iruma?
Worse, Iruma's parents were able to sell him without any consent or even knowledge of the act whatsoever. In most stories with people selling their souls to demons they at least get something out of it even if the deal is lopsided against them. However, the child apparently has zero say if a parent were to decide to sell them to a demon here. It's not hard to imagine humans selling their children to demons to be a common (if as illegal and secretive as child trafficking) occurrence in this universe.
