I have never, ever done anything sexual with an underage girl, and haven't even been tempted until last year. Every year or so I go back to my hometown and visit some friends. For the longest time, they had this awkward,shy, and incredibly introverted little girl (I won't say her name), cute in her own way, but not particularly pretty or popular. But I'm an introvert myself and know that sometimes we need help to come out of our shells, so I took it as my mission to always chat with her, tease her, and make her laugh herself silly. We had a good relationship and she was such a smart little thing. Then one year I show up and instead of an awkward little girl she's suddenly blossomed into an exotic, long legged young beauty. She'd always been scary pale, blue-white practically, but now her mess of naturally curly brown hair cascaded all the way down her back, her mouth was shocking red against her white skin without even a hint of lipstick, long dark eyelashes, pale blue diamond eyes, very slender like a model, but with curves in all the right places, kind of a brunette version of Taylor Swift but way more ethereal and strangely sexy. I was shocked. I chose not to comment on her sudden transformation and just chatted her up as usual while she sat in the back of the car, but I was a little befuddled at a smoldering intensity she now possessed. I couldn't read her at all (typical introvert) and didn't know what to make of her vague smiles. I felt something magnetic going on, but thought it was probably just wishful thinking, handsome older guy/adoring young beauty type of thing. I ended up at my friends place for a movie marathon and by the end of the night, it was just me and the girl. Initially, she was one person over from me on the couch, then when everyone else left, she settled on the floor right next to my feet. After a while, she left the room for a quick break and when she returned, she sat right next to me on the couch. Suddenly, I felt her long leg unmistakably press against mine. We were both wearing shorts and the skin on skin contact was like a jolt of searing sexual energy throughout my body. I was completely thrown off by the experience. There was a moment I wondered about moving away or maybe running from the room before it was too late, but then I thought, fuck it. She's pressing against me, not me against her. I'm just going to sit here and fully enjoy it for whatever it is, no strings. She can press as hard as she likes. It's not like I'm going to jump her in the middle of an exposed space. But I have to admit, if we were somewhere private, it scared me to think that if I made a move on her, I now had the distinct impression she would have welcomed it. But I behaved myself and she snuggled into me even tighter for the rest of a very long movie. What can I say? It was nice. Later when I left and her dad saw me off, for the very first time in her life she blissfully wrapped her slender arms around my neck, murmured sweetly, and gave me a full, tight body hug. I had to do everything in my power to think clean thoughts and not get a hard-on right there in front of her dad. I gave her a warm, open, and affectionate hug back, and bravely at that. The very next day when we all hung out for the morning, she was positively glowing and happy, just beaming radiant joy and confidence. I've never seen her like that. Holy shit, she was glorious. I'm a happily married man, but now I completely understand how adult men can get themselves in trouble with an underage, teenage girl. Under the right circumstances, and when the physical juice is flowing, just about anything can happen. And for the record, I'm glad nothing further happened for all kinds of obvious reasons.