I am interested in this theory and would like more examples and explanations please!
Well the reason i believe this is because of Asta's inability to use magic but repel and take it, in a world made up of magical prowess and strong personalities there has to be a balance, and seeing as how most demon kings exude magic the only way to stop it would be with someone like Asta, also the fact that every time Yuno finds a power to make himself stronger Asta find a power that can counter it and the ambiguity of his grimoire, and last but not least the ending to the last chapter, once the stone were put in place Yuno seem to react to it seeming something akin to an awakening of sorts
oooooHHHhhhhHh ok now it makes more sense, THANK YOU
Yuno is the demon king while Asta is the true wizard king, think about the wizard kings needs to be able to stop a huge amount of magic which the demon king is nothing but I new this would happen thats why Asta cant use magic but he can take it, just my theory though.