A gets free vouchers for golf lessons with a plus one, and takes B.
They begin the lesson and the instructor, male or female, flirts with B, who's too innocent/distracted by golf to notice. A gets jealous as they watch, and silently fumes until it's over, and B has to fuss over them after A explains why they're angry.

Cute and fluffy, I imagine anything with Seto is good for this one :3