Your partner thought to bring a friend but you can tease them both! You start to rub their tits through their tops, comparing the way both of them feel. You can feel that their nipples are hard under your thumbs, showing you that they're enjoying this just as much as you are...

Tease their nipples

Let’s see whose are bigger...

You were hoping to get some help being a tease and your friend agrees to come and heat your partner up with you! Your opponent can't resist touching your chests, making your nipples hard under their thumbs, but they're also very much enjoying the situation.