While Diluc resents the knights of Favonius there was one knight he would never resent, you.

You were now in Angels Share talking to Kaeya and Rosaria as you drank some wine.

Diluc was behind the counter cleaning some glasses, glancing over at you every now and then, getting a bit jealous whenever Kaeya made a flirty remark even if he knew you two just saw each other as friends.