I swing my hips to the beat of the music playing from Sarah's music centre, following my girlfriend's lead, the two of us giggling at our private little 'party'.

We've both dressed up for the party, of course- I'm wearing one of Sarah's party dresses, a soft, swishy garment with a purple pattern on it, and which has a knee-length pleated skirt that flares up every time I turn my body. On my feet are a pair of Sarah's ballerina flats in matching purple (Sarah won't let me wear her only pair of heels as I'm a shoe size larger than she is- and they don't match the dress!), and underneath I'm wearing one of 'my' bras (padded out, of course), a pair of soft cotton panties and a pair of black tights. Of course, I have my wig on, my face is fully-made up, and to add to the excitement further, I'm wearing one of Sarah's necklaces and my fingernails have been painted a very pale red colour! Sarah assures me that the polish will come right off at the end of the day with some remover, and of course, I believe her, but I'd be lying if I said I wasn't nervous at the prospect of having to go home with my nails done up like this!

Sarah's dressed similarly to me, only her dress is shorter and red, and her tights are nude instead of opaque black. Of course, she's wearing make-up and nail polish just as I am!

Once the music has ended, we sit back down on Sarah's bed and share a quick, yet tender kiss, before Sarah grabs my hand and keeps hold of it.

"Do you- do you enjoy these days as much as I do?" I ask whilst straightening my tights.

"Of COURSE I do," Sarah exclaims. "Hanging out with my gorgeous, girly girlfriend? What's not to enjoy?" My body tingles with excitement as Sarah describes me as 'gorgeous and girly'. At school it's not a secret that we're an item- complete with all the good-natured teasing this gets me- but if they knew our REAL secret...

"Didn't you say you had a surprise for me?" I ask, prompting Sarah to squeeze my hand tighter.

"I do," she says with a beautiful sparkle in her eyes. "This is another secret that you must NOT tell anyone, especially my mum, okay?"

"Of course," I say with a nod. Smiling, Sarah lets go of my hand and stands up, turning her back to me. To my surprise, she then lifts the back of her dress and shows me what at first appears to be her bare buttocks, but what I later see have a thin strap of fabric disappearing between them.

"Oh my god," I exclaim as Sarah drops her dress to regain her modesty, "are you wearing a thong? Hang on, are you wearing one of MY thongs?"

"No, this one's all mine," Sarah answers.

"Is it comfortable?" I blurt out, making Sarah chuckle.

"You know it actually is," she answers. "I didn't think it would be at first but after a while you barely even notice it's there." Sarah pauses for a second as her eyes light up further. "Want to try on one of yours?"

"Oh my god, definitely!" I squeak with excitement as Sarah heads into her panty drawer and pulls out the flimsy pink underwear. I inspect it briefly before ordering Sarah into her en-suite. With my whole body tingling with excitement, I lift the front of my dress and carefully strip off my tights, laying them on the bed, before removing my briefs, tossing them into Sarah's laundry basket. Taking a deep breath to calm my excitement, I step into the pink thong and slowly ease it up my legs. My eyes go wide as the thin rear strap firmly wedges itself between my buttocks, but once the initial shock has passed, the thong suddenly feels so... right. After pulling my tights and shoes back on, I call Sarah back into the room.

"Soo..." Sarah says cheekily, "I showed you mine..." Blushing a little, I turn around, lifting my dress and lowering the seat of my tights. Sarah lets out a slight gasp at the sight of my thong disappearing between my buttocks before I pull my tights back up.

"Aww," Sarah says, "now we're thong buddies as well as girlfriend and girlfriend!"

"And you're right," I say, squeezing Sarah's hand, "it IS comfortable." We both giggle as we while away the rest of the afternoon, listening to music, reading Sarah's illicit fashion magazines, kissing, holding hands and comparing our underwear. Eventually, though, the time comes for 'Nikki' to bow out. As promised, the nail polish remover takes care of the colour on my fingernails and my face is quickly stripped of all its make-up. I slowly strip myself off, but before the time comes to remove my thong, I hesitate. With a wicked grin on my face, and Sarah in her en-suite waiting for me to finish changing, I slip my boxer shorts on over my thong and finish putting Nick's clothes back on.

"Ready," I call Sarah, who re-enters her bedroom and immediately makes a beeline for her washing basket.

"I see a bra in here, a pair of briefs and a pair of black tights..." Sarah says with suspicion oozing from her voice. "I DON'T see any pink thongs in here..." I blush slightly and grin at Sarah's piercing gaze.

"I knew I forgot something," I say cheekily. Sarah merely giggles and gives me a quick hug and a kiss.

"You know you'll have to hide it until you can get it back to me to wash it, right?" Sarah asks.

"It's a small price to pay," I say with a smirk.

"...AND you know it's my birthday at the end of the month, right?" Sarah asks further.

"I haven't forgotten," I reply. "AND I haven't forgotten that you want me to do something special for you. I'm assuming you want something more special than 'schoolboy hides the fact that he's wearing a thong from his family'?"

"You assume right," Sarah states. "Make is special enough and even though it's MY birthday, I may just do something special for you!" I grin and Sarah another quick kiss before heading downstairs, where we say our farewells.

"You're in a good mood," mum says suspiciously as I walk through our back door. "Sarah well?"

"She's fine," I say, deliberately talking in a voice lower than my normal one. With every piece of girl's clothing I wear, my voice naturally creeps higher and higher, and with my thong still snugly in place, my natural instinct would be to talk in a falsetto- which would get me in a LOT of trouble very quickly!

"I trust you are still doing nothing illegal?" Mum asks, prompting me to roll my eyes.

"No, mum," I sigh as I head upstairs to my room. Sarah was very clear when we started seeing each other that she didn't want sex until we were both sixteen- and even though that's over a year away for her and almost 18 months for me, I've agreed to abide by her choice. Of course my parents, being the panic-ridden people they are, assumed I'd immediately jump into bed with Sarah and get her pregnant the first opportunity I had.

Once I'm in my room and I'm happy the door is securely shut, I strip off my clothes and inspect the flimsy, yet tight pink thong wrapped around my crotch. It looks so intensely feminine, just like a model in a catalogue or an online underwear shop. It doesn't take long for me to get onto my computer and send a Facebook message to Sarah asking her to buy me some more!

I keep my thong on for the rest of the day and hide it in a small plastic bag to take to school on Monday to give back to Sarah. Sure enough, I see Sarah on Monday and she's happy to see me, but there's a subdued look on her face.

"Hey, Nikki," Sarah whispers to me.

"What's up?" I whisper back, stealthily handing my girlfriend the small bag.

"My mum... found my thong," Sarah explains. "She wasn't happy, but it's more that I lied to her than anything. So I've been grounded for a week, had my internet privileges revoked as well."

"Oh," I say, disappointed that Sarah's punishment means I won't be able to see her at the weekend- and that my 'Nikki day' is cancelled as well. "That sucks."

"Still, the good news is that she's okay with me occasionally wearing thongs, so I can get you some more, just like you asked," Sarah says with a smile. "In fact, given that I don't have PE or gymnastics training today, I'm wearing one right now..."

"Really?" I ask with a grin. "At school?" I glance down at her skirt and tights-covered legs to try to check, but of course there's no trace of the discreet underwear.

"Why not?" Sarah snorts. "It's not like they perform underwear checks, after all." This time, it's my turn to grin wickedly.

"I might have to do that myself at some point," I say with a wide grin, causing Sarah to giggle and grab my hand as we head into form...

The rest of the week drags as I know I'll have to go a whole weekend without seeing Sarah, but I put the time to good use- I've had an idea for what to get Sarah for her birthday, and my unexpectedly free Saturday is the ideal time to go and get it!

There are three more weeks at school- and three 'Nikki days', during which Sarah's tartan wrap-around miniskirt and turtleneck sweater quickly become my favourite outfit- before Sarah's birthday on the 27th, which fortunately falls on a Sunday so I get to spend virtually the entire weekend with her!

I knock on the door, my body tingling with nerves at the sight of all the expensive cars- no doubt belonging to Sarah's extended family- in her driveway. My heart almost skips a beat when Sarah's mother answers the door and coolly ushers me into the living room. Fortunately, Sarah herself is quick to jump out of her seat and greet me with a hug, taking the envelope and carefully gift-wrapped package from my hands. Sarah's mother quickly ushers me into a seat that I couldn't help but note was some distance away from my now 15-year old girlfriend.

Sarah is, of course, grateful for my gifts- my parents aren't rich and my paper round doesn't pay much- and I turn over a lot of my money to Sarah anyway to buy me clothes- but I was able to save enough to get her a pair of earrings, a voucher for a local clothing shop and- because I'm told it's traditional- a mix-tape. Well, mix-CD, anyway. Sarah's eyes light up, though, when she sees the message I've written in extra-small handwriting at the bottom of her card.

You asked me for a surprise, and I have one additional surprise for you. I smile and resist the urge to wink- Sarah still being a year under the age of consent, after all- but I can tell from her expression she's eager to get rid of her family so I can show her my 'surprise'.

The party- if you can call it that- passes ridiculously formally for what is supposed to be a teenaged girl's birthday. Having only been at school for two months Sarah's not really made any friends besides me so it's just her family attending, all high-flying doctors and lawyers. They try to be very polite but I can tell none of them approve of Sarah going out with someone from a working-class background. Inwardly I snigger at this disapproval- if only they knew the 'real' me...

Fortunately, just after 5pm, the family all up and leave, leaving me alone with Sarah and her mother, who is oddly sympathetic to what Sarah and I had just had to sit through.

"I am terribly sorry about that, Nick," Sarah's mother says as I change seats and sit next to my girlfriend. "My family can be awful snobs at times, but I'm sure they see that you're a good boy with a good heart."

"Thanks, Doctor Phillips," I reply.

"Oh please," Sarah's mum says with a warm smile, "call me Beverly.’ Doctor Phillips' is what my parents are called."

"Okay... Beverly?" I say hesitantly. To my relief, 'Beverly' smiles and leaves me alone with Sarah, who eagerly leans over and gives me a quick hug and a kiss.

"Godddddddd," she moans in my ear, "one of these years my family might actually let me be a teenager."

"I thought they were nice," I say, trying to be diplomatic.

"They were POLITE," Sarah sighs. "There's a difference, believe me. Anyway, your card said you have an 'additional surprise'? One I'm guessing you can't show me in public?" I nod, barely suppressing a giggle. "Just so we're clear, if it's a piercing you can't show in public, I'm breaking up with you." This breaks my resistance and I giggle girlishly, desperately trying to keep quiet to keep Sarah's mother from hearing. Unfortunately, my giggling sets Sarah off and we both quickly head up to her room before we give the game away any further.

"Okay, we're alone now," Sarah says.

"Normally I'd be dying to get into a pair of panties," I sigh wistfully, "doubt we've got time for that today. What we do have time for..." I sit down on the edge of Sarah's bed and quickly strip off my shoes and socks, making Sarah gasp and squee at the sight of my feet. There, at the end of each of my ten toes, is a toenail that's been painted a bright red colour.

"Oh my god," Sarah excitedly exclaims. "You weren't kidding when you said 'special'! Sarah grabs me in a tight hug and gives me a quick kiss as I wiggle my toes, much to her delight. "This has been the best birthday EVER."

"I'm, um, kinda gonna need you to go over them with nail polish remover," I say sadly. "I did them this morning but I can't really go home and show them to my parents, much as I wish I could."

"Okay," Sarah says, giving me another kiss before getting a bottle of nail polish remover and going over my toes. "You know, you've done so much for me today, I kinda feel I should give you something in return."

"You, um, do know that's not how birthdays work, right?" I say with a chuckle, earning a playful shove from Sarah.

"I know," Sarah says with a slightly offended voice. "But your birthday isn't until March and I want to do something for you NOW. Well... Not 'now', we don't really have the time. But when you come over next week, I'll have a surprise just for you!" I grin as Sarah finishes her work and I put my shoes and socks back on, wishing that instead of my boring cotton & polyester socks, I was wearing a pair of tights similar to the black pair Sarah had around her legs.

That night my sleep is fitful, restless. In my dreams I'm often in situations where I'm either required to wear girls' clothes or am already wearing them, but since meeting Sarah my dreams have become much more distinct, and my dream tonight will stay with me for a very, very long time.

I'm walking down the aisle at my wedding day, wearing a groom's suit, but as I reach the altar, it gradually transforms, piece by piece, into a pure white wedding dress. There, waiting for me at the altar, is Sarah, wearing a dress identical to my own. As the priest announces 'you may kiss the bride', Sarah and I lean into each other and kiss, a soft, gentle kiss, but one that seems to last an eternity.

I wake up in a cold sweat, my mind racing at a million miles a second and my body completely out of control. I'm able to get myself under control before heading downstairs, but I skip breakfast under the pretense of not feeling well (though obviously my parents aren't keeping me off from school)- if I eat anything with the way I'm feeling now, I'll probably throw it straight back up again.

Fortunately, school passes without much incident, other than my insides melting at the sight of Sarah smiling at me. Even though I've worn her uniform on several occasions, the sight of her in it gets better with every passing day.

Eventually Saturday rolls around and I find myself, as always, at Sarah's front door. When she answers the door, I'm almost disappointed to see that she's wearing my 'favourite outfit'- the same wraparound tartan skirt and purple sweater I wore last Saturday, on top of shiny black tights and warm-looking Ugg boots she'd received for her birthday. My heart rate increases, though, when I see her nails are painted a familiar pale red colour, signifying that I'll have colour on my fingernails before the end of the day.

Once we're in Sarah's room, she sits me on the edge of her bed and heads into her closet. However, when she emerges, she's empty-handed.

"In the past I've always picked out your outfits," Sarah explains. "However, because what you did for me last week was SO amazing- I mean, if you think about it- you went out in public wearing nail polish! So today I'm going to let you wear any item of clothing of your choice. Nothing is forbidden." I grin widely at the news- and there's only one piece of Sarah's clothing I want to choose.

"Didn't you tell me a while ago that you were on the school's gymnastics team?" I ask Sarah, who rolls her eyes and smiles, obviously knowing where the conversation is leading.

"Yes..." Sarah mock-sighs.

"And does that not mean that you would frequently wear-" I begin, before Sarah reaches into her bedside drawers.

"One of these?" Sarah interrupts, holding up a shiny, long-sleeved leotard. "Yes, yes I do. In fact," Sarah reaches back into her drawers and rummages for a second. "I have several!" Sarah holds out four different long-sleeved leotards that I gently run my fingers over, admiring the smoothness and stretchiness of the Lycra material.

"You're not wearing these without underwear, though," Sarah cautions. "And that includes a bra. AND clear tights. And, of course, make-up and nail polish!" I giggle as Sarah tosses me one of my bras and a clean pink thong.

"Do I have to wear a thong?" I ask, curious as to why she automatically went for this 'special' underwear.

"Normal panties are visible underneath the leotard," Sarah explains. "Especially as you're a little taller than I am." I giggle and motion to Sarah to hide in her en-suite as I strip off my ugly boy clothes and pull the thong on, giggling as it tightens around my hips and between my buttocks. I pull on the bra, clipping it behind my back with ease before filling the cups with Sarah's old socks and calling her back into the room. Sarah guides me into the chair in front of her dressing table where I happily sit and allow her to cover my face in her most feminine-looking make-up. Sarah, of course, then applies make-up to herself, before attaching my wig and painting my fingernails a bright pink colour.

Once my nails have dried and I've donned the clear tights Sarah handed me, I pick out the leotard I want to wear. It's bright purple, with shiny silver detailing all down the front, and has a pinch at the front that looks like it'll show off more chest than any of the other gymnastic garments.

"Good choice," Sarah says, giggling almost uncontrollably. "Of course, you'll have to wear the matching scrunchie as well!" Giggling nervously myself, I turn my back on my girlfriend, who lets out a long wolf whistle.

"Nice butt," Sarah teases, giving me a playful pinch on my right buttock that causes me to jump a little. Still giggling, Sarah ties my 'hair' back into a tight ponytail high atop my head, secured with a voluminous purple scrunchie. She then picks up the leotard I chose for the day and scrunches it up until it resembles a pair of panties, which I eagerly step into.

"Now stretch it over your body," Sarah instructs, and I obey, giggling a little as I pull the stretch fabric over my 'breasts'.

"Next, right arm in right sleeve," Sarah orders as I fold my arm back and push it through the sleeve, shaking with excitement as it stretches the fabric out further. I then jump ahead and put the left sleeve on before Sarah smooths out the creases in the leotard so that it sits smoothly and snugly over my whole body.

"And now," Sarah announces ceremoniously as she spins me around to face her full-length mirror, "you are officially wearing a girl's gymnastics leotard!" I'm glad for the extra tightness of the fabric 'controlling' me, as my heart is racing with excitement at the sight of the teenaged girl in the mirror, posing in her leotard with her pink-fingernailed hands on her hips.

"This is- this is- unbelievable," I whisper, leaning toward Sarah and giving her a gentle kiss. "But... Don't gymnasts usually have a team?" Sarah rolls her eyes and grins at me.

"'Team' it is," she says, casually stripping off her sweater and skirt. I turn my back to give her some privacy, but she grabs my shoulders and spins me back around so that I'm facing her.

"Stop being so shy," Sarah reprimands. "I'm used to other girls seeing me change for PE, for gymnastics, this is no different!" I grin, but much to my surprise, it's more at Sarah calling me 'another girl' than at the sight of Sarah stripping down to her bra and thong and pulling on her own leotard. Once she was clad in her uniform, she walked over to me, wrapped her arms around my neck and looked deep into my eyes.

"You've never done ANY gymnastics before, have you?" Sarah asks. Smiling shyly, I simply shake my head. "Good. That means I can teach you!" Grinning widely, Sarah clears a space in the middle of her floor, and for the next two hours she demonstrates various moves and techniques and tries bending my body to match the incredible shapes she was making. Eventually, when we're both sore and tired from our exertions, Sarah calls a halt to the 'lesson' and insists I strip off the leotard, which I reluctantly do, but am exhilarated when she hands me the same skirt and sweater she'd been wearing earlier, which I obviously quickly put on. Sarah, for her part, simply throws a short pleated skirt on over her leotard.

"The leotard was a good choice," Sarah compliments. "Kinda wish now that I'd not quit ballet when I was twelve, you'd make such a cute ballerina!" I smirk at the prospect of wearing what would be one of Sarah's tutus.

"You could always tell your mum you want to start again," I tease, prompting a playful shove from Sarah.

"Tell you what," Sarah says with a wicked look in her eyes, "you come with me to ballet and you've got a deal!"

"I... doubt my dad would approve," I say sadly. "Even if I did the lessons as a boy, rather than what you were obviously suggesting." Sarah smiles at me, but her eyes suddenly become very serious.

"If you could take a pill tomorrow that turned you into a full, 100% girl, would you take it?" Sarah asks. I pause for a second- the question took me by complete surprise.

"Yes," I say, slightly hesitantly. "As long as it also meant that we could still be girlfriend and girlfriend." Sarah beams a wide grin and gives me a tight hug.

"Right answer," she whispers in my ear. But it was at that point that I first began to think: it's not as simple as taking a pill, but people do change their gender. Several people all around the world do so each day. If I wanted to be a girl full-time, I could be. And I wanted to be. But therein lied the problem: Sarah obviously accepted me as Nikki, but would my parents? Would the rest of the world? And more importantly, deep down inside, would I?