You did not recognize the number that sent you the message, or the two guys who’s faces are in the photo, but the bedroom belongs to your best friend. You rightly assume that your best buddy is the owner of the ass that is getting prepped for a fucking. Since the message came from a stranger’s phone, your friend must have given them the number, either willing or unwillingly. And since it’s obvious from the photo, that you will not be there in time to prevent his “pussy” from being ruined, you can only deduce that the message is an invitation to join in the fun.

Thinking it over, you realize that if you help ruin your friend’s “pussy”, he will no longer be your friend. You can’t be friends with a guy you have helped cunt, it’s just too weird. Both of you will be thinking about what it feels like when you shove your thick cock into his formerly tight hole or how good his “pussy” takes a load of fresh cum. Every time you want to hang out, you will be thinking about fucking him. No…if your former friend is going to be a fuck toy, then he will be a fuck toy and nothing more. Just a set of holes to be used. 

You can always get another friend. Maybe one of the guys in the photo.