@CainisLupis Honestly I don't see any holes in the plot so far. One thing I was a little confused on was why Sean would use his sword against the Demora when he had told his student not to use close range weapons on it. However, as I think more about it, I feel like he was acting with emotions (heat of the moment), rather than his training because he clearly cared for Sidney a lot as well. If this is the case maybe you could add something that makes it more obvious?
The different character's you've introduced have added a lot to your world building, and you did it VERY well. You've introduced three different main characters (viewpoints), if I'm remembering right, but not much has been done with one of them (forgot their name atm, sorry). I think the best way to describe this is by saying that the third character seems more detached from the main story and I'm not sure where they're going to fit in at this point. This isn't really a major concern, though, because it's still very early on in the story if you get what I mean.
Your writing style amazes me, though, and it makes the story so much better. I'm jealous! ;)