(Normally I would try to make a really detailed post about this, but it's going to be somewhat limited this time. >_< Guess I'm just not in the groove.)
The first thing Kazuki noticed upon drinking the potion was a strange feeling in his feet. It felt like his feet were vibrating somehow. The feeling intensified slowly crawling up his legs, yet not ever numbing or lessening in the parts of his body that it already was.
As it crawled up his legs he could noticed his feet getting smaller, and his legs becoming smoother, longer and devoid of hair.
The feeling crept past his thighs, causing them to become wider, his butt becomming a little more padded. He could also feel a certain 'plumping' rearrange itself.
It crawled up his stomach tightening it in the process. Soon he could feel it begin in his hands, causing them to become smaller, more dainty and cute. His arms were next as the feeling continued up to his chest.
He saw his arms become hairless like his legs before them. They too became smoother, softer. But the big change was in the chest as he gained two c-cup breasts.
As it passed his neck his adams apple dissapeared, along with a 're-wiring' of his vocal box.
Finally as if it had wasted too much time, it shot up to cover his entire face, causing his entire body to feel as if he was in an earthquake.
His hair, eyes, face. All of it reformed.
Finally the feeling of shakyness stopped.
Though now he stood as a SHE her cloathing had remained the same, causing her to feel rather silly (most likely) Before in a swoop the cloathing altered all at once.
In the end she looked like this:
http://i17.photobucket.com/albums/b84/videomaster21XX/Random%20pics%20for%20web/anothercodesmall3sg.jpg
(Though probably more around the age Kazuki is. Also, the ghost and DS don't come with the transformation. sorry :P)