Ty looked at Mai's dripping snatch and immediately thought of ways this could be improved. Mai, on the other hand, was growing slightly impatient so she began to finger herself and build herself up so that it'd be so much better when her sexy brother came in to finish the job.
Ty thought back to science class last week, when they learned about different stages of Human Life. According to scientists, people had much more sensitive bodies when they're younger. That's why hitting or tickling a little kid will get a bigger result than hitting or tickling a teenager. Coupled with that knowledge, Ty assumed that sex as a younger child would be far more stimulating.
As Mei was fingering herself, she didn't notice her body and proportions shrinking. Her C-cup boobs had shrunk to the smallest A, and her pussy had went to that of a 9 year old, all of her pubic hair receding. Her hair shortened to nearly a bob, and a small about of baby fat appeared on her cheeks, stomach, and ass. Ty, on the other hand, shrunk to a nine-year-old, but kept his 16-year-old cock. He balls and cock still worked like they have been, and so did her pussy despite being so small.
Suddenly, Mei stopped, and took notice of her smaller stature.
"Ty, why aww we smawwer?" she said with a cute lisp.
Ty stroked his comparatively massive cock and chuckled.
"Because younger people are more sensitive, especially during pleasure."
Mai got a very aroused look on her face.
"Ohhh...", she said as she sat up. "Then what are we waiting for?"
With that, Ty pounced on his sister and began kissing her passionately, tweaking her tiny nipples and rubbing her mini-clitty.
After the make-out, Mai decided to position them in a 69 position, with her on top, but she couldn't take in her entire cock, so she nursed it as he went to town on her tiny cunt.
Despite being smaller, Mai still sucked cock like a pro, and Ty came in her mouth, and she greedily swallowed it all.
"Ready for the main course?" she said.
Getting off of him, Mai repositioned herself to fuck him silly. She slowly lowered herself onto him, breathing heavily as her pussy was stretched to the limit.
She went up and down, peppering her movement with "Oh, God! Oh, God!" and obscenities which sounded silly and cute coming from her 9-year-old mouth.
She only got Ty's dick about halfway in, but still tried to fuck it, and mostly succeeded. She was going rather fast now, Ty meeting her some of the way and thrusting a bit.
After 10 minutes and some intense thrusting, she managed to get the whole thing in. She was now on her hands and knees as Ty was under her brushing her womb. He warned her he was about to cum, but she didn't care, and he came inside her. He was right: This was better!
She got off of him, and proceeded to suck his dick some more, getting 2 thirds of it down her throat without gagging. She then laid on her stomach and asked Ty to kindly fuck her in the ass, to which he complied.
Ty knew her ass'd be tight, but not THIS tight. He had to spit on her asshole and part it with his fingers for about 5 minutes, and the simulation was driving her mad.
"JUST STICK IT IN ALREADY!"
And he did.
Ty thrust incredibly hard into her, and she loved every second of it. Her asshole was now super sensitive and it felt great. It took a while for the actual movement to happen, but when it did it was magic to the both of them. Ty came for the third time in her asshole, and when he removed his cock, it came seeping out and some of it went into her pussy.
Despite being covered in crap residue and cum, she still sucked him off, and managed the whole cock in her throat. Ty was now very limp and tired, and the multiple orgasms left her exhausted. She was idly rubbing her pussy while Ty rubbed her tit and rimmed her asshole.
After a few moments, she spoke up, still gasping for air.
"So, what next...hot stuff?"