MITCHELL IS A VAMPIRE!! So he should ping as supernatural non-human. Right now he isn't dangerous but if you want Mithos can pick up on his potential to be dangerous, idk how manasense works enough to really say. It's hard to say what his overall feel is like since he can be pretty volatile, but for now he's pretty stable and nice and friendly.

Yayoi's totally human, Shea is a construct made of psychic energy and the source of Yayoi's domain control (which is like telekinetic energy basically) is the silver ring she wears, which come to think of it is also probably a construct made of psychic energy. She doesn't have any magic herself, but let's say she has a sort of... affinity with the ring? Like it's hers and it won't work for anyone else.