Topic: Magicians. I asked a question on the IRC and while trying to learn the answer, we ended up dredging up a ton of confusion on this subject.
So the PMiSS article on the wiki is a little confusing about some things. First of all, magicians are Youkai, whatever that exactly means. Second, there are two kinda of magicians, those who are born as magicians and humans who become magicians.
Right off the bat. Since when are youkai "born"? I found it an odd choice of words since I always figured they sorta fade into existence.
Third, born magicians aren't actually magicians until they learn "abandon temper" to become ageless.
Why would they need to learn "abandon temper"? If they are youkai aren't they already ageless?
Fourth, for a human to turn into a magician they have to learn "abandon food".
Alright, fine. Does the human also need to learn "abandon temper"? "Abandon temper" almost seems more important.
At the beginning of all of this are my more fundamental question. What happens when Magicians "die"? I imagine, the answer is the same as "What happens when youkai "die"", and I don't know the answer to that either. Of similar importance, what happens when a human becomes a magician and, by extension, a youkai? Finally at the core of it all, what is a youkai?
For the fundamental questions, I think I'm happy with my own answers, unless there just is canon answer that I overlooked.
I've thought about it, and here is what I came up with. I'm going with the definition that youkai are the little things people currently use to fill in the knowledge we don't have. Why are we afraid of the dark, because something is going to get us, and that something is Rumia. I think that's accurate enough. It fits the question "Why is this person not aging or need food?". The answer is that this person is a magician and uses magic.
Finally, my explanation for the transformation from human to youkai is because once the human is, according to PMiSS, "powered by magic" their abilities become so shrouded in mystery, their magic becomes so incomprehensible and unintuitive, that onlookers rationalize their existence as a youkai, causing the human to become a youkai.
EDIT: Note that my answers to the fundamental questions don't address the other questions above. Youkai being "born" still sounds weird, abandon temper still seems unnecessary for born magicians, abandon temper still seems necessary for once-human magicians.