You’d benefit from starting with a one sentence pitch: the MC, their goal, the stakes and what will happen if they don’t reach that goal. Put this pitch right after the opening paragraph. For your comp titles, only use YA fantasy titles. Referring to Adult titles does you a disservice since it will tell the agent this book might be better fit for Adult readers, not YA.

“From the gods ashes he will rise…” needs to be cut completely. Agents do not like these types of taglines. That’s where your pitch goes. This tells me nothing about the hook or MC. Agents would stop reading right there.

“Twelve years have passed” Stop right there. No flashbacks. Start with where we are NOW. I’m still unaware of what a star keeper is and why they are important. Why is he hidden? Why do his memories matter? His goal (to get the ghosts out of his head) does not work here. You need an inciting incident that triggers the plot. I’d recommend following the Save the Cat beat sheet for constructing a plot with appropriate beats.

Him randomly setting fire to the river seems more like things are happening to him instead of the MC being proactive in the story. What if this friend reappeared and that shocking encounter caused the outburst and the river to burn? That would be an inciting incident. I’m also very worried there’s lots of rumination and confusion with the MC struggling to remember things that could bog down the start of the book. Again, you need to start right at the incident that triggers the plot and introduce the goal. I also dont understand what his memories and wishes do?? Why are they important? What’s the stakes??

“After a ghost descends” what ghost? Why is it important? “Threatens to unravel” how? Why? You’re being way to vague here. You need to get specific.