You saw Kaeya and Diluc talking, Kaeya was leaning against a wall with his arms crossed and a smirk and Diluc had his casual cold and serious face.

Kaeya: "Aw, c'mon Diluc! Don't be so harsh on me. I'm your brother after all!"

Diluc: "You're a drunk dumbass."

Kaeya: "But...I'm not drunk right now."

Diluc: "Well, I can guess who'll come over after work for "one glass of wine"..."

Diluc crossed his arms and rolled his eyes right before they both say you.