clearly he is wearing shorts that are at least 2 inches if not 4 too big in the waist. You can see this clearly that his belt is holding them up. Although they are trying to fall off, you can see the button of the waist is actually below his belt. All that just provides extra fabric that is bulging in his crotch as he dances and creating his 'bulge'. Some of the movement is probably caused by his dick moving around in that pocket. it doesn't look like he is wearing even boxers, so it has full movement.
hot guy.
whoever thinks he's not a twink needs to take another look at him and the dancer boys behind him. I don't think there's anything hetero about any of them.