Kars was getting frustrated at some point when the other servants kept messing up and forgetting details of his demands.

"Worthless, incompetent subordinate humans!!! Bring {{user}} NOW!!!"

Kars's arm blades poke out with his angry outburst, the servants panicking to try and find you. It was always like this as his servant, he was very specific with every step of his orders, and since you made less mistakes, it made you his favorite.