An amorphous blob of slime

Sitting on the bed wasn't the humanoid form that Tom had come to expect, but a gelatinous mass of blue slime, the rocky core still floating in the middle. There were no features, nothing human about it, just a glob of slime in a large mass. "Sarah? Is that you?"

"Yep!" Her voice emerged from the slime blob with a slight wobble, but nothing else. No lips, no mouth, just sound reverberating from the mass. "While you were playing with yourself, I've been experimenting~" she called out with silly singsong voice.

He was noticing more and more the way this was changing her. Just like the slimegirls he'd masturbated to, Sarah was acting carefree and giggly, and the changes were only getting stronger with time. "I can see that. Why are you just a blob, though?"

"Just a blob?!" Sarah replied, sounding offended. "Tom, you have no idea what this is like! I'm completely, totally relaxed. I can just...be, y'know? Pluuuuus, not trying to look human means I can do all sorts of neat things. No limits!" As an example, several tendrils started extending from her main mass, waving in the air before retreating into her. "This is just so much...so much better than being a human! I can't even imagine going back to being all solid and meat-y and stuff."

Trying not to feel too worried about hearing that, Tom pointedly stroked his cock a few times. "Well, I'm all hard again now, so we can fuck. Are you going to reform into yourself?" Even as he asked, Tom had to wonder what it would be like to fuck her when she was just a slime blob.