Henry fumbled for the key. Why had he told his father and stepmother that he'd keep an eye on their house while they were away? After a long day at work, the last thing he wanted to do was drive half an hour out of his way to check in on plants and a spoiled cat.
Besides, there was no reason his stepsister couldn't take care of things. Five years younger than Henry, Kirstin was eighteen, more than old enough to take care of the house she still lived in. "She isn't home much," Henry's father had explained when he'd made the housesitting request. "Between her college classes and her job, she's almost never around. Some nights she doesn't even come home."
Surely his father wasn't naïve enough to think Kirstin was staying out all night because of work and classes. But Henry figured it wasn't his place to break the news that sweet, innocent Kirstin was probably out partying. Or fucking.
Henry finally found the right key and opened the door. All the lights in the house were off. All except one. At the far end of the hallway, the family room light was on. Kirstin must have forgotten to turn it off. "Damn kid," Henry muttered.
He headed down the hall. As he got closer to the family room, he heard noises. More specifically, sex noises. "She wouldn't," he thought.
At the doorway of the room, Henry paused. Should he grab whatever kid Kirstin was with and shove him against a wall, or just tell him to get the fuck out? Grabbing could be a problem; it might get him accused of assault. So yelling it would be. Henry looked into the room.
And saw his little stepsister naked on the couch, gasping and moaning as she fucked herself with a dildo.
Henry's cock immediately stood at attention. Kirstin was gorgeous, he'd noticed that before, but her body... God, no wonder she was out all night sometimes. As though on its own, Henry's hand rubbed his cock through his pants.
Fortunately, Kirstin's eyes were closed. "Fuck, yes!" she groaned. "Oh, my god, fuck me!"
Henry went closer, careful not to make any sound that might let Kirstin know he was there. Her breasts were firm and round, a C-cup at least, Henry estimated. A thin patch of blonde hair surrounded her pussy. As Kirstin thrust the dildo in and out of her cunt, she tweaked her nipples. It was one of the sexiest things Henry had ever seen.
He couldn't help himself. He undid his pants and grasped his cock. As he watched his sexy stepsister nearing her climax, he stroked himself toward his own.
"What the fuck are you doing?"
Startled, Henry let go of himself. Kirstin's eyes were open now; Henry had been paying so much attention to the dildo in her pussy that he hadn't realized she'd seen him. "I could ask you the same question," he said.
"I..." Kirstin laughed and looked at the dildo that still protruded from her. "Guess I can't lie my way out of it. I was horny. Got a problem with it?"
"No, but I have the same problem."
Henry went to her and took hold of the dildo. "What do you think you're doing?" Kirstin demanded.
"This." Slowly, Henry moved the dildo in and out of his stepsister's cunt. "How does that feel?"
"You- you can't-" Kirstin let out a moan. "Henry... ah, fuck! Stop!"
Henry let go of the dildo. "You want me to stop?"
"No. I mean, yes. I mean, shit, Henry, you're my brother!"
"I'm your stepbrother, sweetie. Not the same thing." He pinched one of her nipples. "I could fuck you, and it wouldn't be any problem at all."
Kirstin slapped his hand. "It would if I didn't want you to fuck me."
"You're lying there with a dildo in your cunt. You want to be fucked." Henry pushed his pants down so Kirstin could see his cock. "Would you rather be fucked by a dildo, or by this?"
"Holy shit!" Kirstin wrapped her hand around his shaft as if to prove to herself it was real. "Henry, it's fucking huge! You mean I've been living with this all this time and never knew it?"
Enjoying the feeling of his stepsister's hand on his cock, Henry said, "I don't think you would have been interested before. But how about now? Which do you want, Kirstin? Your dildo or my cock."
"God, I'm such a fucking whore." Kirstin licked his cockhead. "I want this."
Henry pulled the dildo out of Kirstin's cunt and tossed it aside. She giggled. "I hope I remember to pick that up afterward."
"Might be kind of hard to explain if your mom or my dad found it," Henry agreed. He knelt between Kirstin's legs and lined up his shaft with her pussy. "Ready for this?"
"I've never had one that big. Fuck yes, I'm ready!"
Henry slid the first inch of his cock into her. "God, you're tight!" he said. "You sure you can take me?"
"Give it to me, big brother!"
With one hard shove, Henry buried himself to the hilt in his sexy stepsister's pussy. She screamed as the full length of his shaft penetrated her. Without giving her a chance to adjust, Henry began thrusting in and out of her. "Is this better than that fucking piece of rubber?" he asked.
"Fuck! Oh, my fucking god! Henry, fuck me!"
"I'll take that as a yes."
Kirstin screamed again, not in pain this time. Henry felt her cunt clench on his cock as she came. It was too much for him. With one last hard thrust, he emptied his balls into Kirstin's wet pussy.
He pulled out and stood. "Feeling less horny now?"
"Yeah." Kirstin grinned. "But it's just a matter of time before I'm horny again."
"You've got your little toy there."
"Uh huh." Kirstin grabbed his cock. "But I'd rather have this again. Good thing my mom and your dad are gone for the weekend."