Vale is used to death-but usually, the people he kills don't come back to life.
Vale's job is to kill people, so when his last two targets get reanimated after he killed them, he takes it personally.
Cyril's job is to reanimate people. His ability as a necromancer means he lives a lonely life, but he's used to it. He's not looking for a relationship, and he's certainly not looking for a confrontation with a professional assassin.
Vale isn't the only person interested in talking to Cyril. When Vale finds goons from a local crime family intimidating the necromancer, he steps in, only for Cyril to freak out when he asks him why he keeps reanimating his targets.
Cyril needs protection, no matter how much he insists he doesn't. It's not Vale's job to provide it, but he finds himself wanting to shield Cyril from the people who want to force him into something he's not willing to do.
He just wishes that Cyril's weird skeleton octopus pet didn't like him so much.