Ty's heart raced at the idea. He'd wondered occasionally what it'd be like if he had been a girl, and having seen Eileen turn from a woman to a man, the prospect had never felt so enticing.
"Trust me," Eileen encouraged him excitedly. "It felt so, so good for me to change- I want you to get to feel it! Plus, I know you'd be so hot."
Ty took a deep breath, then said, "Okay..." He closed his eyes for a moment and focused on the idea: turn myself into a girl.
Instantly an intense shiver ran through him as his hormones began to invert, and he gasped with pleasure. "See?" Eileen said smugly. Ty's skin seemed to prickle all over, and he pulled off his shirt, dropped his cargo pants and removed his boxers, standing before the dark-skinned man naked.
Once Ty looked at himself again, he saw his arms and legs and figure seemed more petite, and that his skin had smoothed all over. Another shiver passed through him as his hips filled out and turned curvy, and he bit his lip as his chest grew sensitive.
He noticed Eileen was now masturbating, stroking his shaft as he stared at Ty's body, kind of disbelieving someone would want to do that with him. He felt his nipples swell, growing to multiple times their original size, and as he breathed heavily, flesh seemed to accumulate around them, which ached to be touched.
"Oh fuck," Eileen gasped. "You're growing breasts!" Ty knew he was right, and it felt amazing- how did Eileen ever not want to have these? Cupping them, Ty whimpered in his higher-pitched voice, and the urge to have them played with or sucked on grew stronger still.
"Mmmh..." a sultry groan of pleasure came from the man watching him, and Ty felt transfixed by his voice. "Just one more thing to change and then you'll be my good girl..."
Girl. Ty was surprised how right that word felt to him now. He peered down at his hard penis, noticing how much less big it seemed compared to Eileen's manhood, and felt the last part of the change take hold.
He felt his shaft shrink back into him, while his balls tugged up inside his body and his scrotum sank into his crotch. And as they transformed, Ty felt the change in gender take root. He would be she, not male but female, not a man but a woman. Instead of filling others with seed, she would get filled with seed.
Once his penis had shrunken to her clitoris, his testicles had formed her ovaries and his scrotum had unsealed to form her vagina, she slowly came to her senses- and saw the handsome, aroused man that was Eileen before her.