User blog comment:AquilaeAltair/OnS Theories. First Theory (Season 2) - Yuichiro, the real Michaela./@comment-36009152-20190528174345/@comment-36009152-20190904193300

That's the thing though, making a deliberate attempt to show Yu eating, acting like any other (if in his own world) child his age talking about growing and playing with toys and that. It was a very convincing display, almost as if he were a normal child... maybe one Sika Madu came across in that time period who was successful in being merged with a seraph, and then subjected to testing hence his forgetfulness.

Alternatively if he is the real Michaela we may be witnessing how such a being acts in this environment. Again came in contact with Sika Madu who then acquired some powers, but with Sika Madu not giving his own blood to Ashera, rather he gave Yu's it does suggest biologically that Yu is weaker than him.

But if he can still be a Michaela if Yu has some diluted blood if that is how it can work.