I (21M) was recently at a Halloween party with my Gf and our friends. We get to the house for the party and all slide our way in through the crowd of people. Eventually we get into the main part of the party and my gf goes to the bathroom with her friend. While she went to the bathroom I couldn’t help but check out all the hot slutty costumes and stare straight at them. After checking out every single girl lol my gf comes back with her friend and we all start dancing and having fun. My gf’s friend was next to us and through out the whole night she kept bumping her ass up against my hand. Mind you she’s in some tight short shorts. After 5 minutes I realize she’s doing it intentionally and while dancing with my gf I let my hand down to the side to grab her ass subtly. She moved closer and started turning so I can rub my hand up her thigh. Eventually she got bumped and I caught her with my hand around her hip and she looked at me with the most sexual eyes I’ve ever seen and said thank you. I held onto her hip and slowly moved my hand around her waist line all while dancing with my gf and she never noticed. Eventually we’re leaving the party and I put my hand behind me so she can follow us and she held on even after we get out of the party. Unfortunately my gf wanted to go home and not stay out so I couldn’t see her at the after party but I can’t wait for next time.