Since spells require mana, how exactly did Iruma manage to activate the Ancient Spell if Iruma doesn't have any magic in him?
Maybe mana isn't required for scrolls.
His grandfather splashed him with the deodorant to hide his human smell and it (seemingly) still seeped through. Does it mean his blood doesn't smell like a human?
The only seeping through occurs when Iruma is hit with heavy amounts of water, like in the water park. When he is cut and bleeding, the perfume likely either blocks the smell of the blood entirely or mingles with it so it smells more like demon blood.
It's weird how all the misfit students seem to be in Iruma's grade. Shouldn't there be other grade misfits?
Either with thirteen trouble makers in the year beyond the normal tolerance of students, the teachers made this unique choice to segregate them rather than let them fester in the other classes and turn them into worse students, or there is a misfit class in each year, but they aren't as notable as the heroes, or the class is broken and no longer a threat, so the teachers move them back to general population.
Animal
How did Iruma know how to dance like Kurumi if he has only seen her dance twice?
One of Iruma's greatest survival traits is his ability to observe and take in information quickly. He would need this to survive some of the things his shithead parents put him through. He is so adept by the time he is taken in by Sullivan, he does it without thinking. He watched Kurumi's dance twice and that was enough for him to anticipate and move in sync with her. It could even be one of his many jobs was some dance performance and had to learn moves quickly, so he would have further experience in picking up dancing moves. Plus, her moves weren't that difficult to do. Strut one way and then back.
