Dodge around the subject. Present it as RP.

"Hey, Sadie."

A noisy slurp precedes her answer. "Y-yeah? Don't tell me I'm doing bad..."

"No way, you're doing great... but... I thought maybe we could spice it up a different way.

"How?"

"Yeah, just a game. Say... motivation for you to swallow."

Sadie scoffs. "I dunno... that seems a bit gross."

"What if swallowing made your boobs fill up?"

Sadie falls silent, but she doesn't stop stroking your cock. She's working through the words, considering it. "That's stupid. Cum doesn't work that way."

"But what if it did? Would that... excite you?"

Sadie squirms a bit. There's no hiding the fact the suggestion isn't killing her mood. You give her a little kiss on her lower lips to inspire her to think faster.

"...Yes. If your cum made my boobs grow. I'd suck you dry." You stiffen in her hand. "I guess that excites you... huh?"

"Y-yeah. I'm surprised about your enthusiasm, that's all."

"I'm just sick of being flat. I wouldn't even care if doing so got me kicked off the Track team. Are you trying to tell me something...? You know a way to make me bigger?"

You search for something to say, some lie... "W-well, I've poked around with the occult a bit. I think iunder certain circumstances we could make you bigger... but..."

You stay calm, trying to make it convincing... in a storytelling sort of way.

"...it's not a subtle process. You wouldn't just get big tits. You'd be huge. Track would be out of the question."

"Interesting," Sadie says, stooping over and sucking you hard.

"C-careful." The lies flow like water. "You go too hard and it'll be irreversible."

That only made her suck harder. One of her bobs pokes past her throat. If only for a second... she pulled it off she deep throated you. That drives you crazy. She must have next to no gag reflex.

You bury your face in her pussy, licking furiously. Every so often, you come up for air, saying a false warning.

"You'll have to buy new bras!"

"They'll be bigger than your head!"

"They'll be super heavy!"

Nothing deters her. Which in your book is pretty awesome. You're getting close and the tell tale throbbing of your cock starts to cloud your vision. Time to break out the secret weapon. Using your bottom jaw you brush your teeth against her clit, massaging it gently and working into a rhythm. Her moans echo in your ears and your own start to bleed out as well.

You... are about to blow.

"L-last warning. I'm gonna... gonna..."

Too late. Sadie thrusts deep on your cock, pushing the head past her tonsils, your throbbing cock pumps semen directly into her throat in long pumping pulses. Sadie's strong legs pinch your cheeks making your already light head spin more. She cums hard splattering you with lady spunk. As a courtesy, you lean forward and drink deep.

Sadie's muffled moans coax a bit more cum out of you, squirting a few more spurts down her throat. You, on the other hand, get overwhelmed and fall back onto the bed. It's too hard to keep your head up. You squint against the gentle squirting. You practically howl with pleasure as Sadie keeps her promise, sucking you dry.

She collapses, sliding off your cock and leaves your exhausted bodies forming a human ying-yang symbol on the bed. She coughs a little but soon settles into calm soothing breaths.

"W-wow... that... was fun."

"Yeah... but... don't say I didn't warn you."

Sadie sat up slow. rubbing her shoulder. "That was a good idea... telling me that little story. Thanks."

"Who said it was a story?" You say, smiling.

She kisses you on the forehead, you catch a whiff of your scent on her breath. "Very funny." Her phone beeps and she moves to scoop it up. She frowns down at it.

"What's up?"

"Fuck. I forgot... Denise says she went home with Terry. Can I... trust him?"

"Yeah. Definitely," you say nodding.

Your word is good as gold. She doesn't argue with you. "OK, new problem. She's invoked roommate right of claiming the room."

"No problem there." You sit up. "I have a vacancy."