As he walked out of the room, he made a quick decision. "I know Sarah is asleep... She went out at night with her friends, so she should be an easy target."
Cracking the door open, he saw his sister in bed, just as predicted. "It's showtime!" He stepped inside, and closed the door as quietly as he could.
Tip-toeing over, he tried to gauge how hard it might be to get in just from a glance. After a few seconds, he decided to just go for it, and see what happens. Once he arrived at her bed, he lifted her blanket up, and was filled with shock. "She's naked!"
He looked her over. She was sleeping on her stomach, but her breasts were spread out on either side. Seeing the massive bumps on her chest gave him an erection, looking at a girl's breasts for the first time. He took in the sight for a few seconds, admiring the large breasts, before making his decision. "I could explore lower... but I think I'll do this."
Taking his clothes off, he hid them under her bed, trying to make it hard to find. Then, he brings himself up to her breasts. Before going inside, he gets a bit curious. "I at least want to check something..."
He put his mouth around one of her nipples, and did a quick suck. To his surprise, there was actually milk in there, and it tasted pretty nice. "Well, I can at least survive off of that if I end up stuck in there."
With a deep breath, he pushed his head against her areola, the top of his head putting pressure on her left breast. His head slipped in pretty easily, and he heard Sarah moan slightly when he went in..