First of all, I am wondering if you mean to spell it "Syrienne" instead of siren? It tricked me for a half second into thinking it was someone's name but I'll blame that on reading too fast.
My initial thoughts from the first chapter are this: Its very intriguing. I will definitely read more but I would like to know a little bit more about the setting, however I suspect that will be in the next chapters.
Let me begin by saying two things; One, I'm only on Chapter 4, and Two, I'm incredibly impressed. The storyline is very well fleshed out, and I LOVE the character of Caia. You've obviously put a fair amount of thought and effort into this story, and it's most certainly paid off. I'll definitely be reading the rest of what you've written, and waiting eagerly for updates. Best wishes, Ike.
My initial thoughts from the first chapter are this: Its very intriguing. I will definitely read more but I would like to know a little bit more about the setting, however I suspect that will be in the next chapters.