Take a slow approach.

"Well," you say. "We shouldn't rush things. I mean, good things come to those that wait. Why not just call it a night?"

Sadie looks at you suspiciously. "What? Just like that? You're not gonna badger me for sex?"

"Nope."

"But you invited me over."

"Because you didn't have a place to sleep. I mean, we can sleep in the same bed if you want, but I'll behave."

Sadie purses her lips and looks at you critically. "You're just gonna plow me in the butt or something, aren't you?"

You laugh. "No way. Fair warning, though, I'm a snuggler."

"OK well, don't get the wrong idea, but I don't sleep wearing pants."

"What a coincidence. Neither do I."

Sadie unbuckles her shorts and lets them drop, watching you carefully for a reaction. "I mean, I did have a long day... so... yeah. I'll take you up on it. Lemme just use the bathroom first?"

No arguments there. You nod and watch her vanish into the bathroom. It gives you plenty of time to write something up in the story. It'll make for a good experiment at least.

Sadie, while crashing over at a friends house, falls into a deep sleep. Thanks to an all night chest massage, she wakes in the morning to find herself with natural Z-cups.

You have your doubts, but when the text turns red, you can't help but grin. You stash the notebook in your night table and wait your turn for the bathroom. You intercept Sadie on the way out, slipping your arms around her slender waist.

Sadie looks at you quizzically but doesn't resist. "What's up."

"Nothing. Just admiring you a little. Is that OK?"

She smiles. "Yeah. You're looking a little hungry. You sure you don't want to mess around a bit?"

"It can wait till morning."

Sadie gives you a little kiss. "What a gentleman."

You step into the bathroom, washing up while fighting back the urges welling up inside you. It's probably gonna be a sleepless night, but one you'll no doubt find worth the effort. You lay low for about a half hour until she dozes off. You can hear her gentle snoring echoing through the room.

You sneak over to your bed, strip off your pants and sidle behind her. She doesn't react to your erection nuzzling against her thighs. You reach out and brush her hands over her chest. She really doesn't have much to speak of, but something tells you that's not gonna last.

The notebook does its job of keeping her in a deep sleep as you fork your hands on her breasts. The growth starts slowly, tickling your palms with her erect nipples. Part of you regrets noting it takes 'all night' but it certainly does a good job of putting you in the mood.

Snuggling close to Sadie, you immerse yourself in her scent. She doesn't bathe herself in perfume like some girls, opting instead to use a simple and clean smelling soap masking the faint smell of sweat. She strikes you as so 'real'. Refreshing in a simple sort of way. You work yourself into a rhythm, sensitive to her squirming against your bulge.

You submit to the urge to kiss her neck, nuzzling her endearingly. It's only fair. I did warn her.

It takes a little over an hour before her breasts have filled into full D cups, massaging them now is rather fun and easy to get in a groove. It's the perfect size to roll in your palm, shifting against the fabric of her shirt. Her nipples don't change much, still rather small and pricking in the center of your palm. It makes for a nice guide to the motion.

You start to doze off, letting yourself 'sleep fondle' your way through the task. Her breasts slip from your hands sometime later. Per the clock, two hours have passed. Her tiny chest is a distant dream, replaced by full F-cups.

You slide your hands down and find her nipples and mash them against her chest. Trying to get back into the groove. You yawn, fighting back the volatile mix of horniness and sleepiness. The massage isn't a chore so much as it really makes you want to push for sex. By focusing on being sleepy you keep yourself in check but you find yourself snapping out of a 'trance' when her tits flop out of your hands and against the bed.

In a daze, you look at the clock. A whopping six hours have passed. Your arms are sore from the effort, like you've been kneading dough for hours. That's not to far off actually.

Her shirt barely covers her now, oversized as it is, she's no match for her... whatever size her boobs are now. You're hardly in the mental capacity to crunch numbers. Undaunted you grit your teeth and go back to work. Her nipples are ig and thick enough now to grab hold of which makes it both easier and more exhausting in one fell swoop.

Before long you nod off and curl up against her. In the distance, you hear chirping birds. Morning. Eight hours later. But you feel strangely rested. The moment your eyes fall shut and you wrap your arms around her waist, Sadie stirs.

"What the--?!" Sadie sits up cradling her now massive tits. "They're huge and... really tender."

You sit up rubbing at your eye. "Well yeah... I worked my ass off all night making them big. Who woulda thought boob magic would be so tiring."

She turns towards you, gaping. "You... did this?"

You nod. "It's what you wanted, right?"

"Y-yeah... but... wow..." She bobbles them, shaking the exposed under boob alluringly. It makes her nipples poke through the letters of her shirt.

"You mind if I..." You reach out. Tired as your arms are, you can't wait to try out your handiwork.

"O-OK... just be gentle. It's weird to say it, but... they feel really stretched out. Like if you're too rough they'll get even bigger."

Perish the thought.