She cleans your butt

"Now let's get your back" she says, her cock still engorged and lathered in soap. You try to rise, so overloaded by stimulation that you would obey her every command at this point, but your legs are like jelly, and refuse to respond to your commands.

You instead lift your hands up to her, entreating her to help you. Sarah lifts you up above her cock and you grasp onto her, you wrap your arms around her shoulders and rest your head as she lowers you down, her cock resting between your butt cheeks. Your own cock resting between your stomachs.

You feel calm in Sarah’s hands, safe from the worries of the world. “Don’t worry Dougie” She whispers, her voice tickling your ear. “I’ll go slow”, as she says this she begins to thrust.

The stimulation is less intense than when she did this to your cock, still, each time the tip of her dick rubs against your anus you feel a bolt of pleasure course through you. Your dick rubs along her shaft, squishing gently against her stomach, which is strangely soft despite having abs strong enough to put the most athletic high schools to shame. You whimper and groan into Sarah’s shoulder. As you lose yourself to pleasure once again.

After a couple minutes of this Sarah shivers then stops, the tip of her cock resting once again against your anus. “Doug?” she asks.

You lift your head and gaze into her eyes, you can see the apprehension in her eyes. Curiosity calms you enough to regain control of your voice. “What is it Sarah?” you ask.

“I was thinking, I’m really enjoying this… and clearly so are you.” She begins to giggle a little bit, you hadn’t noticed but your cock was rock hard again, another record for you. She continues as she regains her confidence. “I was wondering if you wanted to make this more… permanent.” Her cock twitches and you feel yourself clench, the direction this conversation is going is clear as day now.

“If you agree, then that’d make us partners, I’d get exclusive access to you, and, unless you don’t mind sharing, you’d get exclusive access to me.” She blushes as she finishes and looks away, waiting your response.

You understood what she was getting at, once a shemale claimed you, thoroughly fucked you, then all other shemales would instinctively know. While your mother and Crystal would know immediately that you belonged to Sarah (And she to you), other shemales would simply know you were taken, and very few would take interest in you after this point.

This was a life changing decision. On one hand, you truly loved your little sister, you spent more time with her than anyone else asides from Ashley, your childhood friend. But that was the other hand wasn’t it? If you accepted Sarah’s offer then you could never be with Ashley, your friendship would still be there, but it would never develop past that. On the bright side you wouldn't have to worry about being alone in the same room as a teacher anymore, you chuckle a little at the thought.

“Doug?” Sarah asks again, her desire overcoming her nervousness as she snaps you out of your contemplation. You look into her eyes.