This was about three years ago. There was this intern in one of the offices I was taking care of. I was a janitor at the time. She was about 5'6", nice hourglass shape, curves in all the right places, long brown hair, sparkling blue eyes, and a nice set of breasts; a handful, but not too big. We had been flirting a bit over several weeks, innocent stuff mostly. I don't remember exactly how it happened, but we were in the hallway and got on the subject of a set of tunnels, linking several buildings in the complex. I had been through them before. She hadn't. I jokingly offered her a tour some night after she had finished work. Two nights later she took me up on it...
So we waited until roughly 6pm when most people have left for the night. She's dressed in a skirt, button down blouse, heels and stockings, and wearing glasses (I have a thing for glasses). So I open the door to the stairs which lead to a little maintenance shop. I go first to make sure there's no one there then motion for her to follow. We walk over to another set of stairs which lead into the tunnel system. Being the gentleman, I help her down the stairs as they are cracked and worn, and lead her through the first tunnel which is narrow and has a little ditch for the rain. I lifted her at one point to cross over an intersecting ditch and cracked floor, feeling her arms around me, her breasts against my chest, being separated only by the clothes we were wearing. As I set her down, she kissed my cheek and thanked me. Made me blush a bit and she commented about how cute I looked, which made me blush even more. We walked further, our only light coming from small light sockets placed about every 20 feet apart. We came up to a crossroads. Four tunnels, three different directions we could go.
We had just come from the tunnel leading east, so I explain where the north and west tunnels lead. The tunnel to the south was partially blocked off as the company does not own that particular building. But there are still conduits and lights leading that way, so there was enough room at the top to get through if needed. There was also a ledge about two feet high so you could lift yourself over. She looked down each tunnel as I explained them, then walked over to the blocked off one, asked me to help her up so she could get a better look. I held her hand as she stepped up, then she placed my hand on her hip to steady her. I placed my other hand, standing right behind her, looking at her ass, on her other hip. She looked down the passageway for a minute or so, then placed her hands on mine, I assumed to step down. She took my hands and moved them slowly to her breasts. This drew me into her, and my head against her back and her ass against my chest. She looked back at me with a grin on her face to see a bit of a shocked expression on mine. She told me she was moving on in the company soon and wanted to thank me. I have never gotten so hard so fast. She asked me to help her turn around so she could look at me. I did, and she was smiling this seductive little smirk.
She motioned her head for me to step back and I did. She move her hands to her blouse and proceeded to unbutton it, slowly. As she comes to the end, she pulls it from her skirt. The last button undone, she opened her blouse to reveal a white lace bra, which barely covered her nipples. She slid out of her blouse, dropping it to the ledge. Next she unbuttoned the side of her skirt, undoing the zipper, letting it fall to the ledge as well. Underneath, she was wearing white lace panties and a garter, which are attached to the stockings. She looked at me, lifting her breasts and asked if I liked the sight. All I could do was nod, a little shocked at what was happening. She reached out her hands and asked me to help her down. Which of course I do, and she put her arms around my neck and mine around her waist, she hopped down, kissing me. Not just a peck, but a full kiss forcing her tongue into my mouth. At that point I thought what the hell and went with it. I kissed her back, our tongues dancing around each other. Her arms let go of my neck, and started tugging my shirt off, which I gladly obliged. The shirt off, she went after the belt of my pants, then the button, and the zipper. In quick succession, we were there in the tunnel wearing very little. Our hands started exploring each other, mine being drawn to her breasts, hers along my chest.