Agree to make Gwen happy.

You put your arms around her and hold her close. "Oh Gwen, you can make me so happy. And I can make you happy too. Let's go back upstairs."

The two of you head back to your room. The bed is still a mess from last night- it smells of sweat and cum. The smell seems to turn Gwen on.

"Mattie...." she whispers, "I want to save you from the monster...."

Your cock twitches as her whispers become a moan.

"First you have to find the monster," you whisper back.

You lay back on the bed, and she climb on top of you.

"Where did the monster go," she asks, grinning. "It ran away last night, but we didn't kill it!" She runs your fingers under your shirt. It must be here somewhere...” She starts to pull your shirt up.

You wiggle out of your shirt, and she stares at your chest. She runs her hands back and forth over you, and you feel her hips starting to grind against yours.

"If the monster is hiding, we need to show it something that will make it come out," you respond. She grins again, and quickly peels off her clothes. Before you know it, her panties are falling around her ankles, and she's climbing back on you. She wiggles her young breasts at your face.

"Does it want these?"

"I bet it does...” By now you are rock hard.

Then let's find out!" She squeals as she suddenly pulls your pants down. Your cock springs free and she stares at it for the first time in the light of day. "It looks even scarier when I can see it..." she whispers in a low moan.

Seeing your baby sister stare at you like that, you can't help but feel squeamish.

Gwen gently wraps one hand around your heavy member. "Big Bro...." she says quietly, "I want this. I don't know what to do with it, but I want it." Her other hand wraps around it as well. She squeezes and you gasp. She suddenly lets go. "Did I hurt you?" All at once she sounds scared.

"No, it felt so good. It makes me happy. YOU make me happy, Gwen."

Gwen's eyes become as big as saucers. She squeezes you again, and starts pumping like she saw Katelyn do last night. She jacks you harder and harder. Her breathing gets hoarse, and you feel an orgasm welling up in your balls.

You sit up and stop her. "I want to make you happy too, Gwen...”

She blushes, but sits next to you on the bed. You kiss her, and begin kissing her whole body. She puts her hands on your face and you look in her eyes.

"You're kissing me like Katelyn did, Big Bro. I don't want you to do what Katelyn can do; I want you to do something only you can do."

You stare in her eyes for an eternity. Slowly, you lay her back on the bed. Your faces are never more than a foot apart. Silently, your cockhead rubs against her nubile pussy. Her eyes get bigger.

"Big Bro..." she whispers....

You begin to rub your tip between her lips. Her mouth opens as you spread her untouched pussy. You then feel her hymen blocking your progress and start to press through it. Suddenly, as if you've hit a nerve, her legs wrap around your hips and crush you towards her. The more you push into her pussy, the more the winces in pain, the more her legs convulse and pull you in deeper. In seconds, you are in as deep as you can go. As she starts to relax, you start to move and build up pace as she becomes wetter making it easier to slide in and out. A little blood trickles out, but for the most part it seems you won't have to worry about cleaning blood up later.

Her mouth falls open, her delicate breaths gasp through her throat. Her legs no longer touch you, but hang helpless in the air to either side. Her hands are on your shoulders, and her whole body is tensed.

Your eyes have never broken contact.

And you keep moving. Sliding in and out of her as you're pressing yourself inside her, you feel that you're building a bond that can never be undone.

Her gasps are deeper, more ****. Her hips start to thrust against yours in tempo.

You feel the pressure building within you, and you are powerless to stop it. You don’t want to pull out but know that you should. She stares deep into your eyes, and her mouth opens wide as she lets out a gentle, low moan. The sight is almost too much to bare as you try to quickly decide on where to cum.