Adam's transformation - Alpha male?

Adam's state of bliss suddenly changed, the expression on his cum smeared face turned into pain. But that wasn't the only thing.

Sarah could see how his skin started to absorb his and her own cum. Every drop that was still on or hit his skin sank in, got absorbed and disappeared.
Soon no more cum was left, and Adam started to trash around in agony, as his whole body began to change.
Any tiny hint of fat disappeared, and then every muscle and vein, every fiber of his being seemed to expand. If Sarah could trust here eyes, it even looked like Adam was growing in height at the same time.

Soon Adam seemed to be no longer in pain, his whimpering and groaning had stopped, and instead Sarah could hear her brother moaning in pleasure, as the "Growth X" pills began to change him visibly. There appeared clearly defined muscles where before there had been none, on his arms, his shoulders, on his legs. First only a hint, then soon a clearly defined six-pack on his stomach and pectoral muscles on his chest. It didn't take long and Adam locked like a body builder, and only moments later much more than that.

Adam's body was being transformed into an embodiment of male power, a tall man, with bulging and hulking muscles all over, a truly impressive and arousing male specimen.
But Sarah's gaze was especially drawn towards Adam's manhood, as she stroked her own huge futanari fuckstick and stepped in closer.