Two weeks after my daughter Helen graduated, her best friend and my long-time fuck-buddy, Caro, called me out of the blue one evening when I was working late at the office.

"I showed my little sister Kristy all our sex videos, and now she wants you to fuck her," Caro said without preamble. 

My dick sprang to attention when I heard Caro's voice. I'd fucked Caro often but seldom on camera and only ever filmed by my daughter, who had never let me see the videos.

"Helen showed you the videos?" I asked.

Caro giggled. "Obviously. We have girly porn nights watching you fuck me senseless," she replied. "But that's not the point. My sister wants you to fuck her. It will be her first time, so you'll treat her gently, won't you?"

My dick was already hard at hearing Caro's voice, but now it strained at my pants. I hadn't deflowered anyone in a decade, so I hoped to make it fun for both of us. If Kristy was anything like her sister, she'd love sex.

"I promise you'll like her," Caro said when I didn't immediately reply.

"Please," another voice said, slightly higher pitched than Caro's and wavering. "I want you to teach me."

The girl - Kristy, I assumed - sounded nervous, but I could hardly refuse, nor, by the size of my erection, did I want to. I glanced around the office, and it was deserted.

"Sure, Kristy," I said. "I'd love to teach you to fuck."

A few minutes later, it was arranged. Caro and her sister would meet me at my city apartment the following evening. The doorbell rang ten minutes later than agreed, and I felt my dick instantly spring to attention.

I opened the door. Caro was there, holding her sister's hand. Kristy smiled nervously. The sisters wore matching outfits: white sleeveless knitted tops, short pleated black skirts barely covering their bottoms, and black high heels.

Kristy looked very young and was very different from her sister. Caro was tiny, with short dark hair, brown eyes, and almost no boobs. In contrast, Kristy was tall and leggy, with huge blue eyes and long blond hair almost reaching her waist. My gaze was drawn to her impressive cleavage and large boobs, enhanced by a push-up bra. 

I reluctantly wrenched my eyes from her boobs, looked up at Kristy's pretty face, and smiled.

"Come in," I said, taking Kristy's other hand.

I ushered them into the lounge. I opened a bottle of fizz and poured us each a glass. Caro insisted Kristy sit beside me on a sofa, then sat on a comfy chair opposite. Kristy looked uncomfortable: she sat stiffly and as far away from me as the couch allowed.

We chatted inconsequentially for a long time, my cock straining at my pants the whole time. By the time we finished the first bottle of fizz, Kristy had relaxed and moved closer to me on the sofa.

I was about to open a second bottle when Caro spoke. "It's time you fucked my little sister," she said. Caro brandished her phone and theatrically started recording. "I can't wait to show Helen the video; I'm sure it will look great."

I smiled to myself. My daughter's voyeuristic habits were rubbing off on her. But I felt Kristy flinch and stiffen against me. She looked nervous once more and glanced at the camera.

"Are you sure you want to do this?" I asked Kristy, hoping for only one answer.

Kristy bobbed her head and looked down at my crotch. "Yes," she said softly, "but I'm a bit scared."

I turned and gently kissed her. "I promise I won't do anything you don't want me to," I said.

Kristy giggled. "I want to do everything," she said, "and I mean everything, from all your videos. I even made a list."

I heard Caro gasp; I wasn't sure why, but I reassured Kristy. "We can do whatever you like," I said. "I promise I'll be gentle."

I stood, took her hand, and led her to my bedroom, with Caro following close behind.

I pulled Kristy close and kissed her, running my hands down her back. After a moment, she relaxed, and I felt her hands grasp my bum. I lifted her short skirt, pushed my hands inside her panties, and fondled her arse, aware her sister Caro was watching from the doorway with her phoned trained on us.

Kristy responded more fiercely than I expected, pressing herself hard against me, one hand reaching between us to feel my rigid cock. After a bit of mutual groping, I pushed her away.

"Are you going to fuck me now?" she asked, looking nervous.

I shook my head. "Not quite yet. Soon, but first, we need to undress."

Kristy hesitantly raised her arms when I reached out to lift her sweater over her head. Her boobs strained at her push-up bra, threatening to escape and making me marvel that I would soon fuck this gorgeous teenager.

"Keep going," I coaxed her.

I stepped back and started to strip, watching Kristy hesitantly do the same. She slipped off her high-heels and unbuttoned her short skirt, leaving her in a white bra and panties. She wrapped her arms around her stomach.

"I've never been naked in front of a man before," she said. Her eyes were fixed on my crotch. After a short pause, she continued. "Nor have I seen a man naked in real life. Especially one sporting a massive hard-on."

I was down to just my undies. I grinned. "Two new experiences then."

I pulled down my underpants, and my mammoth erection sprang free. Kristy gasped, shook her head slightly, and stepped back. She hit the edge of the bed and stumbled briefly.

Kristy put a hand into her damp panties and started fingering herself.

"Impressive isn't it," Caro said from the doorway. "You'll love it."

Kristy glanced at her sister and smiled nervously. "It's enormous," she said. "It doesn't look as big in Helen's videos."

Though I could see her panties were already wet from her pussy, I wanted to make sure Kristy was comfortable before I took her virginity.

"Close your eyes," I said, "and try to relax."

Kristy complied but stood rigid, looking terrified. She flinched when my hands gently touched her flanks.

"Shhh, it's all right."

I ran my fingers gently over her torso, exploring her fabulous body. Slowly I felt her relax again. When I leaned in and kissed her lips, she opened her eyes and hungrily kissed me back. I wrapped my arms around her and pulled her close so my naked body pressed against hers - my mammoth erection throbbed hotly between us.

After a long intimate embrace, I pushed her away and pulled down her panties, exposing her teenage pussy: a wispy triangle of trimmed blond hair, her slit nestled wetly below. Hairy pussies are the best, though I was surprised she was a natural blond.

I smiled at Kristy, who was flushed and aroused. She looked marvellous wearing just a bra, with her white panties around her knees and her trimmed pussy exposed. As I watched, a drop from her slit splashed into her knickers. 

"You've seen and felt a man's naked body now, and you're almost naked yourself," I said.

Kristy giggled, but I continued. "Have you ever done any foreplay?"

She blushed a brighter scarlet. "No, never," she said, giggling. "I've kissed a few boys." She paused briefly. "But I've used a dildo."

I laughed gently. "This will be another first, then."

I put my hands on her shoulders. "Perch on the edge of the bed," I said, pushing her down.

She looked uncomfortable, with her panties still around her knees, which were clamped together, with her hands covering her pussy.

"It's okay," I said softly. "I promise you'll enjoy it."

I reached down with both hands to remove her panties, then spread Kristy's knees and knelt between them. I felt Caro's naked flesh brush my left shoulder and saw her phone was trained on Kristy's cunt.

Kristy jumped slightly when I ran my hands gently up her thighs until my thumbs reached her pussy. I ran a finger along her wet crack; she was dripping, and the duvet beneath was damp.

I pushed a finger into her tight pussy and tongued her clit as my finger played inside her. Soon, I added a second finger, and Kristy began moaning softly. I felt Caro's tiny boobs press against my back as she leaned over my shoulder with the phone to capture me eating and fingering her younger sister's wet minge.

Kristy's moans got louder and more urgent as my fingers fucked her harder. "Oh god, yes, don't stop. There ... yes, right there," she groaned. She arched her back, and I felt her body shudder as she came, her juices gushing past my invasive fingers.

My fingers and tongue continued their work as Kristy exhaled in a long, satisfied sigh. I felt her hands behind my head. "That was far more intense than with my dildo," she said. 

"Kris, you should suck him now," Caro said. "Stand up and swap places with him."

That was music to my ears. I pulled back from Kristy's wet cunt, looked up at her, and smiled. "So many firsts for you today." 

As we were swapping places, I pulled Kristy close and kissed her deeply, feeling her flushed, lithe body pressed tight against me as I fingered her briefly once more.

I positioned myself on the bed so the headboard supported me. I watched the two sisters kiss. Caro reached down and fingered her sister briefly, then pushed Kristy onto the bed.

Caro stood beside the bed by my midriff with the camera on my enormous erection.

"Go on, suck him," Caro said. 

Kristy knelt on the bed by my feet and stared at my dick. She turned to her sister. "I know it's next on the list," she said, "but I don't think I can.

Caro tutted. "It's not difficult. You've seen me do it in the videos."

Kristy shook her head. "It looks so much bigger in real life. I don't think I can."

Caro glanced around and carefully positioned her phone on the drawers so it still caught all the action. Then she knelt on the bed beside me and slowly took me in her mouth, inhaling my whole length. As always, I was impressed Caro could fit so much cock in her mouth without gagging. She bobbed her head for a couple of strokes.

"See how easy it is," she said. "Come on, you try." 

Kristy came and knelt alongside her sister. I was struck by how young Kristy looked compared to her sister, and I knew Caro was only twenty-one.

"How old are you?" I asked Kristy.

Caro laughed. "Don't worry, she's perfectly legal." She paused. "Eighteen today. You're my birthday present to her."

"Do you like my present?" Caro asked her sister. 

Kristy nodded but still looked hesitant, her eyes glued to my colossal erection, which was now wet with Caro's spit. When Kristy didn't move, Caro took her hand and guided it towards my cock.

Suddenly Kristy jerked her hand back, wrenching it from Caro's grasp. "I can't," she said. Her eyes were wide and still fixed on my bobbing erection. "It's too big," she continued after a long pause. 

Caro reached for Kristy's hand again, and this time Kristy didn't resist as Caro guided it back to my cock. Kristy wrapped her tiny hand around my rigid member. After a few moments, she started tentatively wanking me. Kristy didn't stop when her sister undid her white bra, revealing her perfect breasts. As she continued slowly wanking me, I tweaked her hard nipples.

Caro sighed in exasperation. "Oh, for god's sake," Caro said, "take it in your mouth." 

Kristy wrinkled her nose and shook her head but continued wanking me gently, then she stopped, closed her eyes, and opened her mouth. Caro slowly pushed her sister's head down into my lap. When my hard cock touched her lips, Kristy moaned and shook her head. But Caro relentlessly forced Kristy to take my glans into her mouth. I felt her tongue lick the pre-cum off my cock. After more coaxing, she was slowly sucking me, still with her eyes closed. She was only taking about half my length with each stroke.

"See, I told you you'd like it," Caro said.

Kristy tried to speak, but all we heard was mumbling. She opened her eyes, and seeing my cock buried in her mouth, she shrieked and jerked her head back off my cock.

She shook her head and giggled. She looked up at me. "Sorry, I almost bit you. I've watched Caro suck you on video so often; I should know what to do."

She lowered her head and slowly wrapped her lips back around my cock. Her enormous blue eyes stayed wide open this time and stared at me. 

Caro knelt beside her younger sister and watched critically. "How much can you take?" she asked. "He's the biggest bloke I know, and I can barely get that monstrous thing in my mouth.

Kristy came up briefly for air. She laughed. "I know. Bet I can take the whole thing."

She took me in her mouth again, lowering her head slowly onto my cock, not stopping until her nose was pressed against me and her lips could go no further. I felt her cough, but she held herself still, with my cock embedded far down her throat, for a few seconds. She backed slowly off my dick, then sucked me for a few slow, complete strokes.

She pulled back, letting my wet erection swing free. "I win," she said brightly, with spit dribbling down her chin. "What's my prize?"

Her older sister laughed. "You know what's next. He's going to fuck you, of course!"

Caro turned to me. "Don't move," she ordered. "Kristy should ride you cow-girl first."

This time, Kristy needed no coaxing. I felt my cock rub along her tight teenage body as she crawled up me, on hands and knees, lust written on her face, to kiss me deeply.

I felt Caro's hand around my cock. "Come on, sit up straight, Kristy."

Kristy sat up and slowly impaled herself on my cock, her eyes locked on mine. She was incredibly tight, and I thrust my hips up a few times until I was balls-deep. As she started to ride me slowly, I watched her intent expression. Her perfect tits bounced nicely. 

Once Kristy had impaled herself onto my rigid pole, Caro retrieved her phone and meandered around the bed, filming, ensuring she covered all the angles.

Kristy soon developed a rhythm, lifting herself almost entirely off my stiff rod and then dropping as I thrust upward into her tight, teenage pussy. Her blue eyes were wide with excitement and locked on mine. Soon she was moaning softly, and my dick glistened with her juices each time it emerged from her hot wet cave.

When her moans got louder, I knew she was close to the edge again, and I slammed myself with increased vigour up into her wet cunt. Soon I felt Kristy shudder as she came, moaning loudly. I almost lost control myself.

"Happy Birthday, Kristy," Caro said. "It looks like you're enjoying your present.

Kristy let out a long, satisfied sigh and sat back so her whole weight drove my massive dick as deep as possible and smiled down at me.

"Yes, that was fabulous, much better than a dildo."

Caro laughed. "You know you're not finished yet. There are a couple more steps yet," she said. 

Turning to me, she said, "I think you should fuck her hard now." 

With my cock still firmly embedded in her cunt, I manoeuvred Kristy so she was lying on her back with her knees spread wide apart. I started fucking her with long slow strokes, slowly building up the speed. 

To start with, Kristy lifted her head to watch her pussy swallow my cock, but as I started pounding her hard, my balls slapping against her arse, she leaned back, moaning softly with each stroke.

Kristy became more vocal. "Mmm ... yes ... harder ... yes," she moaned, each word coming when I slammed my rigid pole balls-deep into her tight pussy.

Caro laughed. "I guess you like it hard, then?" her sister asked.

Kristy just moaned louder. Again, I felt her shudder as she came. This time, I came as well and shot my load deep inside her, continuing to fuck her for a few strokes. I kept my still erect dick, buried to the hilt, in her pussy, then rolled us over so Kristy collapsed onto my chest.

"Happy Birthday, Kristy," I said and kissed her deeply. 

Kristy let out another long, contented sigh. "I love your present. It's been the best birthday ever," she said to Caro. "I can't believe I came three times or how hard I came. It's never been that intense before with a dildo."

I rested, exhausted, with my hard cock still embedded in Kristy, who lay on my chest with a contented smile on her face, our noses almost touching, for a few minutes until Caro interrupted us. 

"Come on," Caro said, "you've still not swallowed his cum, Kristy."

Kristy sighed. "I'm comfortable here," she said. "Must I?"

Caro laughed. "You're the one who made the list. It's up to you."

Kristy rolled off me, turned around and straddled my chest. When she leant forward to suck my cock - which was now fully rigid - clean, her red, slightly swollen pussy was temptingly within reach. I lifted my head and greedily lapped up the juices that dripped from Kristy's cunt.

"Make him come in your mouth," Caro said. "That's the best way to finish off your list." 

Kristy lifted her head off my dick and giggled. "What a good idea," she said.

She turned around and repositioned herself to kneel between my legs, facing me, before she wrapped her lips around my stiff rod again. She kept her lovely blue eyes glued to my face as she sucked my cock with long slow strokes, inhaling my entire length.

I never last long when a woman sucks me like that, and sure enough, I came quickly. My hips bucked as I unloaded a fresh load of hot sticky cum into Kristy's mouth.

When my orgasm subsided, Kristy lifted her head and opened her...