For those of you who haven't read any of the books, I'll explain from the beginning. The Chronicles of M series is mostly written in first person perspective. For a lot of people, this is odd. Most books are written in a narrative style and that's okay. Book 4 "Hitori" is written in such a way, but there's reasons for this that I'll get into in a bit. As far as the previous 3 books, and mostly like the next 2 trilogies where M is central to the story, it'll remain first person, most of the time. Here's why.
When I started this series I KNEW I wanted to go first person with it. I wanted them to tell their own stories and be more than just some weirdos on paper to laugh at. Certain back stories would have fallen flat, or maybe never happened had I told it from a third person view. Uhler's story (I won't spoil it) would have been completely worthless from any other point of view. It HAD to be told from his own. Had I done it differently, then the entire purpose of his backstory would have been lost out on. You simply can't understand the personal hell he went through during his transformation without seeing it as he saw it. If that isn't enough, knowing his back story the way the reader does, it becomes pretty clear why he's taken this direction with his life in the present. After all, his story is the BEST case situation. The worst case, the things horror movies are made of, are why he does what he does.
The second reason for first person is, in a way, a two-for-one deal. I knew these characters would change over time. These stories aren't a small section of their lives, it's their entire lives. Sure, there will be gaps of time I won't cover, but it doesn't mean that time missed didn't effect the character. So, by doing it from their point of view I can really show how much they change. Sometimes characters will do the same actions over and over again, but for different reasons. I feel this is a negative to modern cinema that I'd like to avoid, if I can. I'm getting off point here.
The other reason is simple. I'm new to writing. I'm not going to say this was planned. In truth, it was a happy accident. It wasn't until was 1/2 through writing the 2nd book that I realized just how much my writing had changed. Some of it was simply more experience, some of it was experimentation with style (camera angles and such, there's a blog posting on it), but either way it had changed. Even in the third book the style has changed. I feel it's more of a mesh of 1 and 2's style, but we'll see how the reviews come back. What first person allows me to do is to develop my own style through the character's perspectives. Since they are growing/changing as well, so too would their perspective. Where M may take a more poetic noir style now, he may take a more clean, logical style later. It all depends on him and me.
As for Hitori, I went with first person for a couple reasons, but for this topic only one matters - the reader doesn't need to be in her head to get her. In this book, she is (roughly) in her 90's. Since she was 14 years old, she has been the ward and hunter-in-training to Bishamon, god of war. So, for the majority of her life, she has been singlely minded. Her actions speak far louder than her words. When she does speak, she speaks plainly. As such, there's no reason to be in her mind.
By the way, since this has come up a couple times now. Hitori IS Mai. You really think a 1400 year old demon slayer hasn't had a few names in her lifetime? The real question should be WHY is it Hitori, why not her given name and where did Mai come from? Hmmm... :P