Tassel. Dude. I know you’re pissed but nuance is important. Just because you’re jealous and in your feelings doesn’t mean you shouldn’t be diplomatic to Ernon. He is a walking bomb, and he’s not super loyal to your enemy. Plus, if he chooses to come over to their side, it will be solely because of his relationship with Kasia. This is just so not smart from every standpoint.
I really hope he tells the whole story next chapter, or Kasia does. I know their relationship was built on a lie, but it would be a total dick move to act this way and then have Kasia guard him.