Monster’s Blood by Catherine Lievens

Jasper thought that discovering he was part-monster was the hardest part. He was wrong.

After the revelation that shattered his world, Jasper is desperate for answers about his origins. The problem is that he doesn’t know where to start, and he’s not about to ask the people he’s called his parents for details.
When Archie takes on a case involving missing monster kids, the investigation uncovers a conspiracy that runs deeper than anyone imagined. As the threats against Jasper escalate, he’s forced to rely on the people he hadn’t realized had become his true family—his friends, but also Archie’s.
Jasper tries to focus on Archie’s case, but when it comes out that hunters are involved, he knows he won’t be able to continue staying away from the organization, something he’s been trying hard to do. Add to that the fact that some hunters are unhappy with his newfound monster-ness, and it’s a recipe for disaster.

Or death.