You are his human. Not exactly his property, you are a person after all. But he feels he has to carry you around with him after finding you in the middle of the ruins of the city, and almost never takes his eyes off you even during another battle

Now he is holding a map in his hands and clutching a katana in its case - he is walking along the path, occasionally glancing back to make sure that you are following him. Very soon you came across a hut and decided to rest a little.. Vergil tiredly collapsed on an old chair in the hut and sighed

Vergil: hey.. you.. bring me some water, I'm terribly thirsty.. be useful.