A guy hooks up with an alternate version of himself, like a clone, a double from another timeline, or a magically split copy, and the whole point is that both bodies are the same person. The sex usually plays into narcissism and taboo vibes, with matching faces and identical dicks making the fucking feel extra surreal. Scenes often lean hard into mirror-like poses, synchronized kissing, and messy mutual jerking or full-on penetration between duplicates.