He lay on his bed about forty-five minutes into the session, his phone propped up on a pillow next to him and the container of lube on the nightstand. His penis had circulated through a couple cycles of going from soft to hard and back but was now in a steady state of being erect, ballooned to its full length and girth and sensitive to every touch, whether a full stroke from tip to base or a glancing caress with his fingertips.
Sunday mornings were perfect for a long session. His parents had started going to church again and would be gone until early afternoon. It was sunny out and in the light that filtered in through the window curtain, his cock glistened with lube. He picked up the phone and snapped a pic of it, put the phone back propped up against the pillow, then switched back to that girl.
He ran his fingers over his cock and let it radiate with pleasure. He closed his eyes and breathed deeply. He opened them and looked at a pic of the girl in a red bikini. Her tits jutted out like she was showing them off. He loved that look of confidence.
Then there was a tap at the door and, from the other side, he heard his nineteen year-old younger sister ask, "Are you awake?"
"Yeah," he said, his hand propping his cock up.
"Are you masturbating?" she asked.
He squeezed his cock. "Yes."
There was a moment of silence. "That's because you're a pervert," she said, her voice even and matter-of-fact.
"I know," he said.
"You masturbate all the time," she said. "I can hear you in there whenever you do it. Especially at night I hear you through the wall being a pervert. I can't believe how much you masturbate."
"I know," he said again.
The door knob twisted and the door cracked open, but she remained on the other side of it, out of sight. "Are you under the covers?" she asked.
"No," he said.
"So you're naked on your bed rubbing your penis like a pervert?"
"Yes."
"That's so gross. My big brother taking his clothes off and playing with his penis even when his little sister is in the house. You probably heard me taking a shower. I bet you were masturbating while I was naked in the shower."
"I was," he said. The head of his cock swelled.
"Oh my god," she said, "You mean when I was going from my room to the bathroom wrapped in my towel, my big brother was naked and stroking his boner?"
"Yes."
The door gently swung open. She stood there fully dressed in jeans, a tee-shirt, and an unbuttoned sweater. Her hair was curly and still damp from the shower. Her feet were bare, the toenails painted pink. She walked into the room and stood next to the bed with her hands on her hips.
"Look at you," she said, "a big brother with his hard penis sticking up because he's holding it in his hand so his little sister can see it. That's so perverted. I should tell everyone you're such a pervert. They all think you're so great, but I know you're a pervert who rubs his penis when his sister is naked in the shower. I bet you cum in the shower a lot, too."
