Mikaela wiped his memories and everything elese out when he left his angle body, blond hair, for the human one, dark hair, so that the first wouldnt find out hes mikaela even if he searched the yuu's head. Resurrecting him would mean to bring back what he himself already killed long ago.
Of you think about it it was a type of sui***e, since he literally got rid of himself in total.
Thanks how i get it at least.

wait wtf do you mean resurrect mika and use his powers??isn’t yuu mika?? and mika is yuu? like do they mean awaken the power yuu has inside of him?? i’m so confused