Offer to wash her back

"I think that's good, actually," I told her. "But..." I continued, turning to face her. "Maybe I could return the favor?" I lathered another squirt of soap just for the effect.

Alice pondered it for a second, but quickly replied. "Sure! That'd be awesome." And she spun around to show me her back and neck, and her nice round ass.

I couldn't help myself and gave her nice ass another slap.

"Hey!" Alice yelped before giggling.

"Can't help it!" I replied back, grinning, while beginning to wash her back.

"You really love my butt that much?"

"Well of course!" I said. "Considering there's not much else to look at."

"You're just jealous because you could never twerk." She scoffed playfully.

"Just because it's a good size doesn't mean you can twerk," I counter.

"Oh," she says looking back with a sly expression on her face. "Watch me."

Then she put her hands on the front wall of the shower and bent over, and started shaking her ass. The cheeks bounced up and down playfully, evident of how much she worked to have it toned, and it was one of the hottest things I had ever seen. I tried my best to keep my hands on her back, but she was slippery and moving too fast. Before I knew it, my hand slipped and fingers ended up someplace warm.

"Ohh," Alice moaned, as her twerking halted. Then she froze, realizing she had moaned aloud. She looked back at me, her face bright red. I looked down to see where my fingers had ended up, blushing just as hard.