My parents took in foster children when I was a kid. This continued for some years, with an array of kids passing through. I was 19, almost 20 when this situation took place. Two sisters, Lyn and Melissa, had lived with us for a year or more. Lyn was the younger, by about a year. She was short and slim, not much body to her, but nice. Melissa, being older and more developed, had smooth curved lines, lovely hips. Her clothes indicated also a beautiful set of boobs. I was about 6 months older than Melissa, almost 20, but still totally naive, especially where sex was concerned. We weren't close friends, but tolerated each other, got on okay as had to be the case in a family home.
One day, Lyn and I were sitting in the kitchen, each doing our own thing. The kitchen was the centre of the house, the warmest place in winter, the place where the family met, chatted, worked.
Lyn nodded to me saying "Your store's open." I realized the zipper of my trousers was open.
Taken aback a bit, I tried to recover. I said "So, maybe you'll just have to go in and see what's on sale."
She kind of threw back her head. "Oh, you wouldn't dare let me do that."
I said "You'll never know, because you'd be too chicken to try." It wasn't that I was trying to goad her into something. Instead, it was because I figured that, if she thought I was scared, then she would lord it over me, mock me for my fear. And there would be no quick end to that mockery. She would also tell Melissa, and they would both have it over me. I couldn't let that happen. I was quite sure she wouldn't do anything, wouldn't have the courage. To be honest, I was pretty sure I didn't either. She jumped up and went out of the room.
Over the next few days, I caught her occasionally glancing at my crotch. Once, she saw me catch her glance. She blushed, turned away. At one point later, as I walked by her, I said quietly, as much to keep her off guard as anything, "The store can be open if you're not too chicken to look." She gave a 'humph', and walked away. A couple days later, again walking by her, I repeated it. "If you're too chicken that's fine. If you're not chicken, just touch my crotch. I'll come up to your bedroom and you can have a look at my store. Of course, if you're too chicken..." I left the rest unsaid. She didn't say anything, just turned away. I was still very sure she wouldn't do anything, but at least I had made sure she couldn't hold my fear over me. It was safer that way.
A few more days went by. Nothing. That was about what I expected. Then one day as we were standing at the sink washing dishes after lunch, I moved behind her, to the other side, to pick up the next pile to put in the sink. That put her slightly in front of me, slightly to one side, part of her hidden from anyone's view. She dropped the hidden hand from the plate she was drying, and touched the front of my trousers. I was almost in shock. Was she really saying she had the courage? I doubted it but thought I'd never know if I didn't follow through, find out. The question of courage was now totally in my court.
She raised her hand, returned to drying dishes. I didn't say anything, just carried on with the washing. But my heart was racing.
When we were done, she hung up her towel, and announced "I'm going up to my room to do some homework." And away she went. I wondered what to do. Clearly, I couldn't let her think I was now the one chickening out. But I also doubted she would follow through. I decided to follow her, so announced that I too had homework to do, and headed upstairs.
I went to my bedroom, removed my underwear, put my trousers back on, with the zipper left open, and walked to her room. The door was closed. I took a chance, walked in without knocking. She was sitting on the edge of the bed, a book in her hand. I walked over to her. She put the book down. I said "Well, here's your chance."
She looked at my trousers, kept her eyes off my face. She was nervous. I can't say I wasn't. Then slowly, tentatively, her hand reached out, touched my zipper, paused, then slid inside. There, her fingers touched my cock. It jumped. I think she did a bit too, drew back, then slid in again.
Still not looking at my face, she felt my cock, took hold of it, and pulled it out. Then she let go of it, looked at it standing erect. Finally she took hold of it again, fondled it. I thought I was going to cum right there. That would have been embarrassing, but fortunately I managed to hold back.