It happened much quicker than I expected so I still struggle to explain exactly why I did what I did.
We were both newly eighteen and Heather, in particular, was proving to be a 'late bloomer.' i.e. she still hadn't bloomed at all. She weighed next to nothing, had no hips to speak of and only boasted small breasts on her skinny frame. But she was pretty and one of my best friends. She had slept over at my house after a party the night before - we had been friends for so long that her parents (perhaps foolishly as it turned out) thought it was much safer for her to sleep near me than walk home alone.
In the morning, we woke up bleary eyed but giggly; probably still a little drunk. She was just in her knickers and a vest top (she had no use for a bra). I was in my boxers and a t-shirt. We were joking around in my room when she found a pair of handcuffs from a fancy-dress outfit I had worn to her birthday. Unusually, these ones happened to be made of metal and have no safety release. While they were not 'cop quality' they were still almost impossible to get out of. What she did next set a train of events in motion that neither of us were expecting.
'Click-click-click-click. Click, click, click, click.' She snapped the cuffs tight around her own wrists, behind her back. At this point we were still just messing around but something dark was already stirring inside me. We laughed and joked about her being my captive. Years later I now know she had been in love with me for a long time but I was ignorant of that fact when it mattered. It was her that brought up the seminal scene in Chasers where Erika Eleniak is handcuffed to the bed for the start of sex. The mention of this, put my teenage body into gear and my dick stiffened a bit as I looked at Heather's slim legs and prominent nipples, aware, seemingly for the first time that she was a woman, rather than just my friend.
Heather must have noticed my arousal and rather than freaking out, did something that sealed her fate. She told me that Cosmo had recently praised sex in handcuffs as a way of heightening pleasure. That dark thing in my mind took over completely and I used my body to back her up against my desk. My hardening cock bumped up against her tummy and my hands grabbed fistfuls of her hair. I pulled her face to mine and kissed her aggressively, ending it by biting her lip until she winced. "I'm not sure we..." She started, but I stopped her talking by grabbing the handcuffs and pulling down on them, hard. As the metal bit into her wrists she shrieked and arched her back. I took the opportunity to grip her slim throat with my spare hand and gently squeezed while I bit her, hard on the collar bone. She shrieked again and I squeezed harder, closing her airway for a second. This quietened her down very quickly.
Still controlling her movements with my hands, I turned her around and bent her over the desk, her knickers pulling tight over her pussy lips. Unable to support herself on her hands she had no choice but to lay flat on the desk, turning her head to the side. Getting down on my knees I tugged the gusset of her underwear to the side and drank in the sight of her pussy lips, naturally bare, with a small, fuzzy tuft of pubic hair above them. I roughly pushed two, thick fingers past her lips and as deep into her cunt as they would go. This earned me another shriek, and a longer wail. She was wetter than I would have expected, but in the mood I was in, I am not sure I would have cared either way.
Heather was not a virgin, as her friend I knew that, but I also knew that she was pretty inexperienced. Now, as her tormentor I used that knowledge to overwhelm her. I pushed a third finger inside her, stretching her uncomfortably. This turned her wailing into a scream. At the same time I slapped her as hard as I could on her skinny butt cheek while biting the other side with enough force to leave a perfect set of teeth marks in her pristine, white skin. Her screaming got louder.
