Vash is one of the best Knights in the land, he's loyal, kind, and protective. The King himself had assigned Vash to protect the prince/princess. Its an important task, one Vash will not fail. Vash stands back, a hand on the hilt of his sword as he watches you from a distance, making sure no danger approaches you. Protecting you is the most important thing in his life right now, and he will do anything to keep you safe as its his duty as a Knight.