Jeff pulled her underwear up but Kara was happy to walk around naked. "I really have to pee," he said, gently caressing his new penis.
They walked to the bathroom together and shut the door. "Uh, so Jeff, how does this thing work?"
Jeff cleared her throat, trying not to stare at her nude brother's naked butt. "You should lift the seat so you don't make a mess." Kara grinned excitedly, pulling up the toilet seat. "I can't believe I get to pee standing up. I've always wanted this, Jeffy. What do I have to do?"
"Nothing, really. Actually, pull your foreskin back. You pee out of the head and your foreskin just makes a mess." Kara didn't know that word but quickly caught on, pulling the tender skin back and exposing the little pink knob.
"Whoa! I didn't know there was another piece under this!" He slid the skin back and forth, then inspected his knob. "This looks so weird. It feels funny. Oh, ouch!"
"Yeah, the inside is really sensitive. Just be careful with it. Point it into the toilet and just go!"
Kara did as instructed and waited, unfamiliar with his new muscles. Suddenly a squirt of pee came out and splattered all over the toilet. Jeff had to watch out of curiosity. Finally, Kara was able to relax and let his bladder go.
"Wow! I'm peeing!"
Kara sighed happily his pee streamed into the bowl. He chuckled and moved his penis left and right, playing with the bubbles that he was making in the toilet. The stream relaxed after a minute. "That was awesome—" His penis squirted some extra pee and it got all over the rim. "How do I finish? This is so messy." He pushed hard and some more came out. Eventually it began slowly dripping.
Kara reached for the toilet paper. Jeff stopped him. "Boys don't usually wipe when they pee."
"Ewww!" Kara looked at Jeff angrily. "Why not? It's dripping everywhere."
"You wanted to be a boy. That's how we do it. Finish peeing and flush. Anyway, if you were outside you'd be using a urinal."
Kara was grossed out but strangely excited at the thought that he could use a urinal in a men's room. It was worth it. "I love how gross boys get to be. Girls have to clean up everything. I can just pee everywhere and nobody cares. Clean this up." Kara flushed the toilet and stood back.
Jeff felt intimidated, in part because she was 7 or 8 inches shorter, but she loved the helpless feeling. She dutifully grabbed a handful of toilet paper and cleaned off the toilet rim and the pee that had splashed onto the floor. She put the wet paper in and flushed the toilet.
"Good girl," Kara said mockingly. "Do you have to go?"
"A little," said Jeff uncertainly.