As someone who has finished the Novel, I can assure you that Dohyun is not a red/black flag, and his mistake is not as bad as the spoilers out there. This is why you should read the novel until the end idk why they called him manipulative but i never find that side of him in the novel, he never gashlight Wooyeon or anything. He aplogize properly. And his POV is soo funny and sad at the same time...