"You really want it huh?" Emily says rubbing her clit.
"Well then, the birthday boy will get what he wants." Emily said before she started to masturbate.
You start to do the same thing with a bit more speed hoping to cum. You kept stroking and stroking your cock with a quicker and quicker pace. You cum and paint the insides of your sister's pussy white. You see her juices rising so you go for round two. You soon finish and her juices reaches your stomach.
Emily starts to masturbate faster and harder, making the juices rise quicker. You keep pumping yourself until the juices reach your neck and her vaginal walls are coated white with your semen. Once the fluids go over your head you can feel your body liquefying, and Emily going faster. You feel immense pleasure as you're being dissolved almost orgasmic, just like Emily. Whenever Emily finally came your body was fully dissolved and was nothing but her vaginal juices spewing out into the bathtub as she screamed in orgasm.
The tub nearly flooded with Emily's cum, but she didn't care. She was lost in the afterglow. For a while she was out of breath.
Until finally she regained her breath and said. "That was amazing! Thank you little brother for giving me this gift on your own birthday. I hope you enjoyed your present as much as I did."
She rubs herself a bit more and then rubs one of her breasts. She noticed that her breasts and ass became a bit bigger. She bit her lip, enjoying the new changes and decided to go for round two.