It happened on a Wednesday. First, information was gently inserted into everyone’s mind, information about what would soon occur.

Going forward, people between approximately the ages of eighteen and twenty-five would undergo a sort of second puberty: they would develop into fully functional hermaphrodites. The majority of people will have this hermaphrodation occur between twenty-one and twenty-three, with only about five per cent having it occur before twenty.

For males, this would take the form of developing breasts, loss of chest hair above the bottom of the rib cage, a slight widening of the pelvis and the growth of a second reproductive system, a female one. This process generally takes six months, though breast development may continue sporadically well into one’s late twenties.

For females, the main physical changes would be mainly limited to simply developing their male reproductive system, with few or no other visible changes. Development of the male reproductive system generally takes only three to four months for females.

These, however, are only the most common outcomes, and the tail of possibilities is long. For instance, it is entirely possible, for example, for a male to end up with an entirely feminine appearance by the end of this second major sexual development period. Or the opposite for someone born female, or anything in between. A person’s desires can have an influence on this, for example, a closeted trans woman is more likely to end up with a feminine appearance. These outliers may take a year or more to fully change into their new appearance. Though the majority of people do follow the rules above.

The last thing that changes is sexual preferences, those attracted to men gain an interest in breasts on men. Everyone gains new urges and reflexes related to their new parts and mostly gains an interest in the parts they were formally uninterested in. These are again generalisations, other outcomes are possible, rarely some may find their orientation changing, some may become bi, others may go from straight to gay, or the opposite, such cases would be rare.

Everyone ends up with a dual libido, that is, it is possible to be aroused with only one’s male parts, or only one’s female parts. In fact, at some point, their body will “lock in” to one or the other, releasing a pheromone signal that will cause their partner to “lock in” to the opposite. Once someone locks into female “mode”, their male parts would pull almost entirely into their body to get them out of the way, much the same way they do in the cold.

The change that came was that everyone in the world would be altered as if this had always been the case, so those over twenty-five would all rapidly change into the hermaphroditic version of themselves, and those between eighteen and twenty-five would land at some level of development of their new characteristics.

The warning given also included information that, at least in this initial change, people’s relationships would be taken into account. So it would mostly avoid leaving those in love unattracted to their partner.

Remi sat and nursed his wine, digesting the fact that he had struck out with another woman.

He had come to Paris in hopes that its reputation for romance would help him. It had not. The information about the coming change had given him hope. Perhaps if he got big breasts, like the woman across the café, he would stand out more and have a better chance.

He felt a strange pressure on his chest. Ah, it begins! He felt a rapid surge of weight and began to hope that his secret wish was being granted. Then there was a strange sensation, a pulling sensation in his groin, behind his balls, a strange sensation in his guts. He noticed his pants start to tighten around his hips as his pelvis changed shape; they shifted from a relaxed fit to tight on his butt. He felt the strange sensation of his new parts between his legs. It was a strange thing. He shifted slightly in his seat and sensed the effects. Some of his newly-acquired parts slipped past other parts, even inside himself.

As the growth of his breasts subsided, he could feel the heavy fullness on his chest, the motion as he shifted slightly, the new tightness of his shirt. It filled him with hope. He looked down and was disappointed: these were not the large breasts he hoped would make him stand out. He glanced around the room at the other men. Sure, they were by no means small, even noticeably above average. But a bit above average would not give him the eye of ladies as he walked into a room. He despaired.

Julie sat watching Remi. She had seen him leave another woman’s table in obvious disappointment. She had seen the rapid growth of his breasts and felt new feelings of… interest in them. He had been decent looking, to begin with, but the way his breasts sat—perky, plump, so round, and with no support—they were stunning breasts. She understood things about what makes a bust nice that she would never have thought about before. Her own were significantly larger than his—but, in her mind, not as magnificent. They sagged slightly because of their size; his were full and firm. She found herself staring at him, giving him a second and third look, not just at his chest, but all of him. The addition enhanced his look and made him all the more attractive to her. As much as she looked at him, she could not stop her eyes from returning to his chest. She found herself crossing the café, approaching his table, doing her best to ignore the strange sensations of her own newly formed parts and the lack of room in her underwear.

“Bonsoir, is this seat taken?”

Remi looked up, seeing the woman of his dreams speaking to him. As he lifted his gaze his eyes passed up her body, and he felt himself pause on the new bulge in her pants. This too felt strange, it was, he found, not an unwelcome sight, in fact, part of him very much liked it.

He was aghast but managed to answer.

“No, no, by all means.”

A conversation began; they were enchanted, and everything clicked. Both had trouble not looking at the other's chest. At one point, they both looked at the same time and caught each other as they looked up and broke into laughter. They talked and talked until the café closed for the evening.

Lucy sat at the table waiting for her date. They had been texting for over two months after meeting online. She was falling for him even over text: however, they lived just far enough apart that it took long enough to drive to mean any date needed to be planned. They had both been busy and this was the first time they both had a free evening. As a result of the change earlier in the day, she’d had a very busy afternoon and had been unable to check in with him. At 24 it was very likely he’d changed too… so it should be OK, at least she hoped.

Still, she fretted about what the change might have brought for James. The nerves got to her, not just first date jitters but the change being so new it brought her a whole set of new things to worry about. What if he’d come out looking feminine… she didn’t think she’d gained an interest in women, or he’d been turned gay by it…

“Oh, there she is. Thank you.”

She looked up and saw James had just finished talking to the host. He quickly walked over and sat across from her. He looked exactly the same as he did in the pictures. No breasts. Her blood ran cold. He hadn’t changed.

“So…” James said, he sat down, “Crazy stuff with the change, huh?”

“Yeah…”

“Are you OK? You sound… worried.”

She took a deep breath and mentally prepared herself. “I… changed.”

“Ah.”

“Are you… OK with that?”

“I… think so. I wasn’t thinking anything was going to happen tonight…”

“Yeah, but you didn’t change and… it takes months…”

“Right… uh… If you’re OK with me, um, not doing anything with your new bits until… I’m into it, I think I’m OK.”

Relief washed over her, she felt herself relax, he liked her enough to be OK with this!

“There is one other thing…”

She stiffened again.

“Sorry I’m being awkward, I just feel weird talking about this in public, and on a first date.” He paused for a moment, “I’m not… totally unchanged, I, well there’s a bit of the start of things showing… down below.”

“Oh!”

The waiter chose that moment to arrive to take their drinks order. After placing it they were both silent for a few minutes before James spoke.

“So, you’re still attracted to me even though I don’t have...” He very obviously glanced at her chest.

“Err… mostly? I obviously don’t have much experience with what I, um, like yet, but I don’t think I’m picky about uh… bust size. How… did you think to check that you were part, well, changed?”

“I just… felt something weird when everyone else changed and had a little look when I was getting changed to come hare, I needed a hand mirror to see. I can’t really feel it right now, I only felt something shift when the change happened. What’s it like for you?”

“Feels weird as hell, none of my undies fit comfortably, there’s a reason I’m wearing a long dress.”

His eyes went wide. “So, you’re… going commando?”

“Didn’t have much choice, all my undies really don’t have room, at all, like things spilt out.”

“Ah.” He paused. “I seriously wish the, uh, whatever it was more specific about timelines. I do feel a bit weird about you having a, you know… I think it’d be easier if I were into it…”

“Believe me, it’s weird for me too. Thinking about actually using it weirds me out, as did seeing a guy who had changed for the first time… It feels so weird to, well feel that way about boobs.”

“I wonder when what I like will change, before or after the new equipment is ready? I kinda hope sooner.”

“Really?”

“Well only because of what you’ve got…”

She felt herself blush and felt arousal in both her parts. She steered the conversation away from that topic and by the time their drinks arrived they were chatting like the world hadn’t radically changed and she felt almost normal. She had a lovely time.

Vanessa thought about the last three months since the change. She hadn’t changed on that day, despite being 28. Her husband did. At first, they were both uncomfortable with the new situation. He hadn’t changed much visibly if he had clothes on. His breasts were very modest, just enough to show through a loose shirt, his hips hadn’t noticeably widened. She was fine with that.

It took some convincing to get him to be around her naked again. She was still attracted to him, it helped that she was a tad Bi. At first, he did everything in his power to avoid his female sexuality, so even after getting him into bed a week after the change it was mostly normal. Then came the lead-up to his first period, his female libido was thrown into overdrive.

The whole time was a lot for both of them. Her doing her best to help him learn what he needed to know about his brand-new parts and trying to get used to having “lesbian” sex. She’d never been with a woman. It was awkward like they were teenagers doing it for the first time again.

Once they got past the initial awkwardness it became fascinating to her how differently he responded to female arousal, to her touch while he was in female mode. The way he moved, it was sometimes like a woman had possessed him. When he was on that part of his cycle he even started walking a bit more feminine, swaying his hips. It became very easy for her to tell when he was female horny.

He also got much, much better at foreplay on her as he got more familiar with his own female parts, better at getting her going, and much better with his fingers.

She had joined a study on the change as a subject after her doctor examined her. They obviously wanted to know what was different about her. It turned out she wasn’t alone, though there weren’t many like her, only 1 in 500000 people. They sequenced her entire genome as part of the study, it turned out that everyone who had not changed shared a genetic marker. Effectively she had a rare developmental disorder that would have prevented hermaphrodation if that had existed when she was the right age, at least that was the theory the scientists told her. She worried about her kids; would they be like her? Would it cause them social problems?

For her hiding that she hadn’t changed was easy, just don’t mention it, but her son… would he have trouble dating in university?

Dr Theodore Davis shifted uncomfortably in the chair, he felt the slight movement reflected in his breasts, still, after three days he was still very strongly aware of their motion. They weren’t especially large, but they still jiggled, despite the bra his wife had insisted he wear. The reporter interviewing him had finished the question, something about if he knew how the change was possible. He didn’t enjoy interviews, but his position meant he had to give them.

“No, I’m afraid I have no idea how it happened. Nor does anyone else. However, it’s the most exciting thing to occur in my entire career, it means there’s more we don’t know than we ever thought! Did you know that there were several reports of male doctors who thought to stand on their office’s scales while they changed, and they reported that as their breasts grew their weight increased? As a physicist, this is evidence that things we thought were rock solid, are not. Conservation of mass? Perhaps not! Perpetual motion? Might be on the table. Though none of that means much if we can’t find any of how our current theories are wrong, all we know right now is that they are.”

“Do you have any idea where to start?”

“None whatsoever! Maddening, isn’t it? Clear evidence that we’ve clearly missed something very significant in our understanding of the universe, but we can’t recreate it to study it. We’ll have to hope one of the many ongoing experiments shows some unusual data. Maybe one of the neutrino detectors or something. We’re checking data from every instrument that might have been turned on at the time in my lab. I expect every other lab is doing the same. I’m somewhat jealous of biologists, they at least have a general idea of where to start looking to update their field after this, we in physics don’t have much to go on in terms of where to look.”

“Are you upset that you’ve been wrong all this time?”

“Not at all! Science is all about what we know now. Throughout my career, I have been wrong many times, about what the result of an experiment would be, about mathematics and all kinds of things. For example, at the beginning of the twentieth century it was becoming clear that much of what was thought about physics wasn’t quite right. From that time, we got Relativity and Quantum Mechanics. This is much bigger! It’s clear we’re more wrong than we thought possible! Now we’re left to figure out what is more correct! Nobel Prizes will go to whoever makes even a small step toward finding that. Just the tiniest thread to pick at could be the discovery of the decade!”

Selected Frequently asked Questions and Answers about Hermaphrodation

General

• What are these answers based on? The answers given here are based primarily on the first 2 months of data from three ongoing large scale international studies. One of university students that after the change were partially along the hermaphrodation process, the second of people who fully changed, and the last on people who did not change at all but are old enough that they were very likely to start hermaphrodating soon. All studies involve following participants with daily questionnaires, weekly MRIs and blood tests to establish baselines and how hermaphrodation progresses. As the studies are all ongoing the data is preliminary.
• How long will it take to go back to normal after my body switches to male/female mode? How long going back to neutral mode takes varies a fair bit from person to person and over time, sometimes a person might have sex or masturbate and be back to neutral 15 minutes after they're done, other times it can take a few hours, even if they aren't aroused at all for that time. There is no known action you can take that will change the time it takes.
• What do I do if my body is in female mode and I have to pee? Gently pull on the head of your penis, if not enough is outside of you you can gently get a finger and thumb into your body. It should come out without discomfort, you will need to hold on to it until you begin urinating at which point it will not retract until a few minutes after you stop.
• I’ve found myself having strange sexual fantasies about things I was previously uninterested in? What turns on each half of you can be different, so you may be discovering what works for your new libido. For example, many men strongly associate breasts with femininity so it's common for men for whom breasts are erogenous to have breast stimulation more strongly arouse their female half. This is less common in women, they tend to associate breast stimulation with sex and foreplay in general, not specifically their female parts.
  For some the kinds of fantasies that they enjoy as a male are totally different than as a female, for others, they are very similar.
• I have found one side of my libido is much stronger than the other? Some people may find that their new libido is much stronger than their original, or the opposite, it is entirely possible that you may discover that one side of you simply has a much stronger sex drive than the other.
  It may also simply be related to your menstrual cycle, the balance in strength of your male and female libido commonly varies during your cycle. Generally, for a few days before and during the most fertile part of the cycle your female libido will become stronger and your male libido weaken, or even disappear. During and after a period it is common for the opposite to occur, that is the male libido waxes while the female one wanes.
• Can I accidentally get myself pregnant? There hasn’t been a known case of this occurring, so the answer is likely no, but there is also no known mechanism to prevent it if you get semen into your vagina.
• I seem to be changing more than normal, will I look like the opposite sex? If so, will I get taller/shorter? It’s possible, some rare people do change to an appearance that is of the opposite of the sex they were born. It is not expected, based on current data, that you will get shorter, as most people are nearly fully grown at the age that hermaphrodation occurs and for the most part development doesn’t seem to reverse growth. Getting slightly taller may happen for women whose appearance is becoming more masculine, but it is uncommon.

For Women

• I got an erection for no reason? Once a woman’s penis develops sufficiently she will begin to have spontaneous erections, like boys going through puberty they are likely to be fairly frequent for a few years.
• How big will my penis get? There does not seem to be any significant difference in the size of women’s penises and men's, nor is there any known correlation between penis size and other body parts in women. None of the studies conducted took data that could be used to make any statements about the heritability of penis size in women.
• What are the signs I’m starting to hermaphrodate? The general first sign in females is a significant increase in sex drive and some mood effects, though many women notice nothing until the first external signs of penis development occur.
• How will things progress when I start changing? The first stage of hermaphrodation in women is the internal formation of the testes and the internal parts of the penis and related structures. As those parts develop the head of the penis will form externally followed by the scrotum as the penis grows. From there, things simply grow and develop. Once the penis is partially formed and generally just long enough to aim while urinating, the urethra in the vulva will close and urine will begin to exit from the penis. Initial changes to sexuality were generally noticed around the time of their first erection. For straight and bisexual women this first part of their changing sexuality is feelings about breasts on men. Homosexual women, almost universally find changes to feelings about penises on their partner to be the first noticeable change to their sexuality.

For Men

• How do I know when to expect my first period? If your female organs are still developing you can expect your cycle to start about two months after your vulva stops developing. Your internal female organs begin developing first and the external parts only start when the internal parts are nearly finished.
• How big will my breasts get? Look at your parents and siblings. Breast size is not significantly sex-linked, male and female children of the same parents, when fully developed, tend to have proportionally similar breast sizes. Normal genetic variations obviously happen but if you have a sister it is likely that your breasts will be of similar size, in proportion to your bodies.
• My hips seem wider. Is that normal? It is common for men to have their hips widen as their body changes. Most do not end up as wide as a woman of the same height would be likely to have. It is expected that this may mean men who become pregnant and carry the child to term are more likely to require cesarean birth than women.
• What are the signs I’m starting to hermaphrodate? The usual first signs are related to internal changes. The evidence available points to the development of the womb, ovaries and related structures as the first stage, and that may make significant progress without being noticed. As the ovaries form they may cause hormonal effects that can cause some of the same kinds of things as puberty, including some mood swings and acne. At around the same time, the development of breasts begins with the formation of breast buds, as in girls during puberty. The order is not entirely consistent, sometimes breast development is delayed until after the first external signs of the vagina appear, which does not happen until the internal female reproductive system is very nearly complete.