Well the way they are portraying puppy-kun is that his social media status is a lie. Like, his life is a lie. He isn't actually popular, he isn't sociable, he just fakes it for the likes and the sponsorships. It is easier to put up a facade online. Instagram for the most part is just for show. So I can somehow believe something like this could happen. Although it is actually a really bad thing that it does because the seme is bad bad news. And he now has power over Puppy kun's life. If he gets upset he could spread all those pics of him online and make his life worse. I mean puppy kun literally hides away because of a photo of him cross dressing, I can't imagine what could happen if his nudes were leaked.
This is kinda like not believable at all.. well a lot of yaoi like stuff that dont rlly happen irl but they still make it make sense. If hes a famous social media star wouldnt he never reply or send a pic to that sort of message?? Seems dumb