Yup, I think most of the tension is from Kazuya's side, buuuuut considering in game all the angels tried to suppress humanity's free will and tried to kill him, I suppose you can't fault him for his caution. He'll get over it quickly enough if he deems that Gabriel isn't going to kill him whenever he turns his back.

He's cool with pranking and trolling - since he hangs out with his Loki who is, well, Loki.