He gets jealous:
Damon- You and Damon were at the grill most likely drinking and playing pool. Damon had left your side for one minute when you saw an old friend,
"Y/N? Is that you?"
You turn around to see Jay, your old friend.
"Jay? It's been too long."
You go up to Jay and give him a hug when you hear a cough from behind you. You turn and see Damon glaring at Jay.
"Damon this is Jay, my old friend, Jay this is my boyfriend Damon."
Jay extends his hand for Damon to shake but Damon rudely declines by grabbing your waist and pulling you in for a kiss. He kisses you passionately showing that you are his. He pulls away and smirks at Jay.
"Back off she's mine."
Damon goes over to the bar and you say your 'goodbyes' and 'talk to you later' and go over to where Damon is sitting. You were mildly ticked off by Damon's personality.
"Damon, what was that?"
Damon looked over at you and took the last swig of his drink and he stood up. He placed his hands on your hips and he pulled you closer and leaned down to whisper in your ear,
"Your mine and don't you forget it."
You couldn't help but giggle at Damon being jealous. He straightened up again and looked you in the eye.
"You know you're quite sexy when you're jealous."
You wink at him. He smirks,
"I know."
You roll your eyes and take his hands off your hips,
"And also quite cocky."
He kisses you and you wrap your arms around his neck and he wraps his arms around your waist. He pulls back and smirks.
"But you love me anyway."
He sticks his tongue out at you and you do the same. When you get home he shows you that your his, and only his.
Stefan- It was a quiet afternoon at the Salvatore boarding house until Damon decided he wanted to have some fun with you.
"Hey Y/N."
Damon walks out only wearing a towel causing you to whip your head in the other direction. Damon chuckles and continues,
"You know you want this."
You roll your eyes even though he can't see your face.
"No Damon, you want me, not the other way around."
You smile but you knew Damon was going to do something.
"Cocky much Y/N?"
You smirk,
"Very much."
Damon definitely makes you laugh which is probably why Stefan was so jealous. Stefan glares at Damon,
"Go get some pants on Damon."
Damon rolls his eyes,
"Way to kill the fun Stefan."
Damon leaves to his room to put clothes on and Stefan comes up to you with a hurt look on his face.
"What's wrong Stefan?"
He looks away but you tilt his head so that he's looking at you again. He sighs,
"I want to make you laugh like Damon does."