You had me with the first line. I was intrigued. Though not much happened in terms of the story, the first part was fast paced and a quick read.
My only major complaint: Nana-san has funny talk.
I didn't care much for her speech pattern. It felt too Mulan-ish. I almost got the impression you'd seen that movie one too many times.
Apart from that, I'm eager to jump into book 2. You've got a great bunch of characters. You set things into motion, now I need to see how everything plays out.
I'm off to go write a book review.