Venti was your ex, after you guys broke up he started dating someone else. But he didn't seem to actually like her?

One day while you were at Angels Share talking to Diluc, you felt like someone was staring at you. You look around to see Venti with his new girlfriend sitting on his lap.

For some reason Venti looked upset and jealous, you didn't think much of it. Diluc then asked if you wanted anything else: "Would you like anything else?"