...i mean, with all they had been doing, Iruma becoming a demon is the natural course for things to go...
But man, IDK. It feels so utterly boring, with Amelie right besides him, for the story to decide "nah, Iruma is never going back to the human world" and then trying to shut people up by showing the jingling keys that is him turning into a demon.
Like, FUCK. There is so much fuckin shit to do with that concept, it was being teased since the start of the arc, and LITERALLY NOBODY expected it to be more than just a short stay in the human world...yet the entire thing is shot out of a cannon into the stratosphere, together with all the self-reflection and potential activities for Iruma and Amelie to do in the human world together, with the consolation prize being a plot development which was only not obvious (as in, it wasn't the exact 1st thing that came to mind for plot progression... it was the 2nd), but besides that was predictable and natural, yet it's not even a thing that left significant changes in Iruma's body, because we can see in the last panel that they were mostly starting to revert.
MAN WTF I'M SO FUCKING PISSED! I hope at least the fingers do remain as claws, because that's the only not-reversed changed by the end of the chapter besides the fang. Make him actually visibly different now, instead of subtly looking different, if we're not getting an actual decent arc of Iruma having to deal with the human world one last time.