By reader demand I've added a third chapter. I liked the build up of this story, so resisted it going all the way for two chapters. You will enjoy this more if you read one and two.
*****
The next day, a Saturday, Sam was half asleep in his bed when there was a soft knock on the door at around ten am. He had been having a dream about the various ways he wanted to participate in rampant violations of Massage Club Rule 3 with his sister. While massage club allowed a variety of erotic interaction, from whipped cream 69s to shower massage, Rule 3 was always obeyed. Rule 3 stated that there was absolutely no touching of the private parts during the massage.
"Come in," he called out.
His sister Katy walked in, wearing the familiar black silk robe. "How ya' doin brother," she said softly.
"Exhausted," he said. "Too many fantasies keeping me up."
"Yeah, me too," she grinned. "Listen, I was just thinking. Our parents don't get here until late this afternoon, maybe we could, uh, have just one last Massage Club adventure."
Sam woke up fast. "I'm intrigued, what do you have in mind?"
She didn't answer, and instead took his hand and led him out of his room and into the shower. Without a word, she turned on the water, slipped out of the robe, and guided him inside. Once they were under the water, she leaned into him and wrapped her arms around him, holding him close. He put his arms around her and stroked his hands up and down her back. They stood their holding each other in the warm water for a long time.
After a while she reached over and got the massage oil, and poured a ridiculous amount of oil in between their bodies. Then she slid her body up and down against Sam's spreading the slick oil in between them. His hard cock quickly became covered in oil, and it felt amazing sliding across her oily body.
Then she turned away from him and put her hands up on the wall, bending forward slightly and inviting him to rub his cock on her ass. He stepped forward and put his hands on her hips, lining his hard cock along her ass crack and sliding it up and down. He poured more oil on her back and watched it slide down onto her ass and his cock. He watched mesmerized through the steam and splashing water of the shower as his cock glided through the oil and spread it around on her ass.