You find yourself subconsciously drawn towards the dragon's nether region. Though it takes you a little while to venture all the way around his enormous body, the sight you see when you arrive fills you with shameful lust.
Outstretched before you are the dragon's sheathed member and his puckered anus. Of the two, the anus appears to draw you towards it more. You venture over to it. Though surrounded by gleaming scales, the anus itself is a ring of soft, pink, puckered flesh. You caress it slightly with your hand, causing it and the dragon to shudder involuntarily.
"Hmm... an odd choice, mortal... to become my anus, with no function save the discharge of excrement from my body... This is what you wish, eh?"
In response, you caress the soft flesh again, harder this time. It shudders once again. You feel a surge of embarrassment, mingled with raw lust. "Oooh...very well!"
Quicker than you would've thought possible, the dragon's great muscular tail wraps around you and shoves you feet-first into the dragon's anus. The soft flesh squeezes you as you sink into the dragon's body.
As your neck reaches the pink flesh, your head involuntarily cranks upward. You black out for a few seconds as your face expands and contorts. You lose all feeling in every part of your body except your face and throat. When you regain sight once more, you see nothing of the dragon except for his massive tail, which is attached just above your "face." Your lips are clenched into an "o" shape, and you can feel the strong pounding of the dragon's great heart somewhere above and behind you. An odd taste works its way into your "mouth." You are unable to move anything.
"My, but you turned out better than I'd expected. Enjoy your new life, mortal! You will be serving me for centuries to come!" His massive tail relaxes slightly, blocking most of your vision. You'd be panicking right now if int weren't for the lusty emotions and heat coursing through your mind.