Tell her off

"Ugh stop it Cassie!" I said, "I can see everything!"

I didn't get the impression that she was trying to arouse me, she was literally showing me her butthole, this was just Cassie's crude and immature way to do something obnoxious and rile me up. Like mooning as a prank but taken to an absurd degree.

"I can do what I want!" she said, then laughed maniacally. "You got a problem with my butthole?"

I sighed. She was still bent over, spreading her ass cheeks, giving me quite the lewd view. Well, two can play at this game.

"Uh you know you gotta shave back there too? I can see your butthole hairs," I said to embarrass her, although it was a true statement.

"Oh my god shut up you pervert!" Cassie said, standing up quickly. Aha! I actually had managed to find a little bit of shame on my bratty little sister.

I laughed. "Don't show your butthole if you can't take criticism about your butthole hairs," I quipped, "Old Chinese proverb."

"You're a moron," Cassie said, standing with her back to me.

I was all covered in soap so I pushed her out of the way, avoiding the obvious places a brother shouldn't touch. I also had to angle myself so she couldn't see my boner, which was unavoidable in this situation.

I rinsed off in the warm water. Damn, showering with a woman did feel good even if it was my sister. I shouldn't think things like that, but it's true.

"Okay, I can't see back there so you'll have to tell me if I'm getting them," Cassie said. I turned and she was bent over, angling a pink lady's razor between her buttcrack. Butthole on full display again as her compact, curvy body bent over in front of me. Okay, I retract what I said about Cassie having shame.

"And I'm the pervert???" I said, naturally objecting to serving as spotter while my sister shaved her butthole. And yet, she was totally naked, shaving her most embarrassing part... and letting me watch. As much as I hated to admit it, this lined up very closely with a certain perverted fetish of mine. Of course I could never let her know that. Maybe I could just pretend she wasn't my sister. After all I couldn't see her face from this angle. "Okay fine, but be quick about it."

"Spread my butt cheeks," she said as if this were a totally ordinary request to make to a brother, "I can't shave my butthole properly otherwise."

I sighed but couldn't resist the invitation. I touched her fleshy cheeks and spread them, exposing her anal rosebud more clearly than ever. I was rock hard. But I was imagining this was a hot girl I knew from school, not my sister. So it was okay. Yeah, sure.

Her asshole was almost winking at me. It was so tight and clean, with the water flowing over it. Nothing like seeing a girl's butthole, even if she is a total tomboy. Her nimble hands shaved along the side of her buttcrack as it sloped down to her hole. She was being careful, obviously not wanting to cut herself there, and I suppose her **** hand control skills from gaming had an unlikely application here. But she couldn't see what she was doing.

"You missed a spot, back, up higher," I said. Part of me was hoping she'd ask me to touch that spot, the way I had to do to find missed spots when shaving my face, but she got to it on her own, all bent over and contorting herself to shave her butthole.

"There, is it totally hairless now?" she asked. I spread her wide and leaned in to give it a close inspection. Man, it really was hairless now. It looked even better than the high-res porn I'd looked at online... geeze, I shouldn't have thought that.

"Y-yeah," I said softly, "It's hairless."

She wiggled and I reluctantly released my hands from her ass cheeks. She stood up and flicked her hair back so I got splashed with cold water. Always a brat, this one.

"Now that I'm making money maybe I'll go get some Korean bitch to wax my cunt and butthole in a salon. Geeze can you imagine doing that for a living?"

She laughed at her tasteless comment and waddled into the water to rinse off. I had ended up under the shower head because I didn't want to brush past her in my current state, which included a rock hard erection. In fact, she was blocking the door. She was bound to see it, and if she did she'd never let me live it down that I'd gotten a massive boner from watching my sister shave her butthole.

For the moment, her back was too me as she rinsed her backside. I had only one choice. I had to jerk off and get rid of the erection.

I didn't have to think, since Cassie could turn around at any moment. I gave myself a few quick strokes with my practiced hand. I thought it would take more than that but perhaps because of the urgency of the situation, I came almost immediately. It was all I could do not to groan as I looked at my sister's bare backside and round butt as I had an intense orgasm with my cock in my hand. Ropes of cum shot out and I aimed for the spray of the shower so it could wash my sperm down the drain harmlessly.

My erection was already going down so I was relieved, but then I looked and saw a wad of my cum had landed right on Cassie's back. Before I could react, she spun around, shamelessly showing me her front side, covered in soap suds.

"Get outta the water Mike!" she yelled, "I did that soapy thing you like now I'm gonna rinse off."

"Okay okay," I said, "Be sure to rinse off your back too really good."

"Stop mansplaining!" she said in her obnoxious way, "A lady knows how to clean herself!"

"What lady?" I asked as I laughed and stepped to the back. I was soft by then and the abundance of water had whisked away all of the cum from my cock. As long as she rinsed her back I figured I was in the clear. The embarrassing glob of semen mercifully washed off her backside.

"Don't be a moron!" she said, spinning around, most of the soap gone now from the spray of the water. She gestured to her body which, I had to admit, had all the signs of being feminine.

"Okay so you're female, but that doesn't mean you're a lady. Do ladies also show their buttholes to their brothers?" I quipped. Hey, I have to give back as good as I get, it's part of being a brother.

"GET OUT OF THE SHOWER YOU MORON!" Cassie yelled at me. Still, she didn't sound the least bit hurt by my words, or I'd have felt bad. This was just our usual sibling bickering... except we were naked.

"But I'm not in the shower, remember? This part back here is out of the water so it's not the shower, according to you," I said. She pounded a fist against her other hand and looked at me with a violent gleam in her eyes. To avoid being murdered I quickly stepped out and grabbed a towel.

"That's what I thought," she said cockily at having scared me away.

I chuckled and dried myself off. What a strange life I lead.