The guards watch him, but they don't stop him. It seems like they know who he is. Bull is with Cyril when Vash shows up and he watches with his arms crossed.

Cyril gets up and goes to his sons, greeting them with a wide, happy smile. He takes one of them and kisses the boy's head before doing the same with the other. "Come on, let's go a private office. We can eat there."

He doesn't invite Vash to his room because he shares it with Marikoth and he knows Marikoth would probably hate Vash being there. Instead, they end up in a guest room that has a small table in it, they can have lunch and tea there.