Thank you! I wasn't really looking for any massive criticism, but here are the answers to your questions:
1) No, the entire story takes place in Ingoun.
2) There are three major characters aside from Noa in Ingoun. One is a guardian, another is a longtime friend and the third is a killer phantom that's trying to befriend her.
3) There are some antagonists here and there that definitely get in the way of Noa's actions (such as other phantoms) but the story will mainly focus on the messaging element and the mystery of what is beyond Ingoun.
4) The phantoms. They want to devour Noa.
If you have any other advice, then I'd be happy to hear it. Once again, thanks.