That's kinda lame appear out of nowhere convenient solution
I mean I wouldn't say out of nowhere
Maybe a
bit contrived but the carrot has been there, also it makes sense that the magic lesson that started this would be the thing that gives iruma the inspiration to end this conflict.
After all the point of the arc is that the many ears shouldn't have to rely on only their hearing and that nova is going to be the future king of the many ears because of his kindness and hard work.
That hardwork paying off is hardly out of nowhere.
But I do think this was rather fast paced. Probably had to move the arc along somehow?