Before Kyle could answer, Erika held a finger to his lips. "Wait a minute before you say anything, Kyle. There's... something I've always wondered about... and it's something I'd like to try. Please?"
How could Kyle refuse? He was curious now, anyway. He wondered what Erika could have in mind-- well, aside from sex, obviously. So Kyle remained silent for a minute, until Erika finally said, "Alright, it's been a full minute, so you get both."
"Okay," said Kyle. "What do you have in mind?"
"I've... well... I've always kind of wondered what sex would feel like, if the roles were reversed." Erika blushed. This was obviously something she was self-conscious about, although she wasn't too embarrassed to bring it up in the first place. "So, for your transform, you're going to turn into a girl-- a female version of yourself, to be more specific. As for your dare... as soon as you're done transforming, I dare you to ask me transform or dare. When I choose transform, I want you to turn me into a male version of myself."
Before he could react, Kyle could feel his body changing, getting slimmer and curvier. His hands and legs became feminine. He watched in disbelief as his flat chest grew into a pair of perky B-cup breasts. He could feel it even in his face, which was itself becoming slimmer and more ladylike. His hair grew longer, until it reached his shoulders. Then, finally, the big change happened, and he felt his balls pop up into his body and his manhood shrink down into a tiny nub, until it had completely changed into a clitoris. At last a slit opened up, with lips on each side where his testicles had once been.
After a few seconds of panting from the rush of adrenaline that had been released during the change, Kylie finally regained her breath and asked Erika, in a much higher, girly voice, "Your turn. Transform or Dare?"
"Transform," said Erika.
"Very well," said Kylie. "Turn into a male version of yourself."
Erika's transformation began just as quickly as Kyle's had, and just as she had imagined, it seemed like the exact reverse of what she had just seen. Her hips and buttocks lost some of their curvature, and her torso became boxier. The muscles of her upper arms and legs grew thicker, and her fingers lost their girlish frailty. Her hair shortened, and she even grew some thin patches of stubble on her chin and upper lip. Her breasts dwindled into puny A-cups, and then into nothingness as her chest went completely flat. At last, she felt her vagina seal up and bulge as it became her scrotum, and her clitoris more than double in length as it changed into a penis. When it was all over, she was a he, and he was satisfactorily endowed.
"How do I look?" said Erik.
Kylie smirked. "Like someone who's just about to have a really enjoyable half-hour." She giggled and pulled off her shirt, revealing her bra. "Shall we get started?"
"Mmm," said Erik, taking off his own shirt. "I thought you'd never ask."