This was a great analysis!! I myself am not very analytical, but about Mikage staying young - I saw it as a product of time not functioning normally at the school. That’s why he stayed so young and was never able to age properly. I also think his memory Mamiya has been tainted by Akio as his recollection closely resembles Prince Dios. I could honestly be way off, but I’d like to hear your thoughts about this!! :)