In the medical world, it got called the Hormone-Oriented Sexual Transmutative Disease. The disease was transmittable through sexual activity and, as its symptoms and causes became more well-known, it got classified as an STD (Sexually Transmitted Disease) very quickly.

Many people were fearful of the disease. They were never sure if they'd catch it, nor how severe its effects would be, except that they could catch it through unprotected sex. They'd avoid any irresponsible activity whatsoever, but there was never complete guarantee that they'd be safe that way. On the other hand, there were also people who actively sought to catch the disease, to become a so called "Host". For some, after all, the changes they may face as a result of the disease, could be beneficial for them, even if permanent. The biggest seekers were women, as well as a great portion of transgender communities, because of the assurances that parts of their bodies would turn into those of the opposite, or the preferred sex. Then there were the men who tried to avoid it, and who wished to preserve what they had, and what they knew was in their benefit.

The consequence of this imbalance, especially the increased activity of women in sex culture, was cause for an ever-growing list of patients who became carriers of the HOST-Disease. The STD quickly matched other such illnesses like Herpes and HIV in its virality and frequency.

The disease is more popularly known as the 3S-Disease, as per referral to its three predominant components of physical manifestation to the human body: Sex, Shape, and Structure. These are the ways in which parts of the human body could change as a consequence of catching HOST-D. These changes are oriented around the lower body (below the navel) or the upper body (above the navel) separately, and they could affect both men and women. These changes are listed as follows:

• Sex.
• Upper body: increased sensitivity in the chest region and a rise in pitch to the voice for males; decreased sensitivity in the chest region and a fall in pitch to the voice for females.
• Lower body: development of female sexual organs and loss of male sexual organs in males; development of male sexual organs and loss of female sexual organs in females.
• Shape.
• Upper body: development of breasts and shapely figure, decrease of bodily hair growth and a softening of the skin on the upper body for males; loss of breasts and shapely figure, increase of bodily hair growth and toughening of the skin on the upper body for females.
• Lower body: redistribution of body fat to ass, hips and thigh regions, decrease of bodily hair growth and a softening of the skin on the lower body for males; redistribution of body fat from ass, hips and thigh regions, increase of bodily hair growth and a toughening of the skin on the lower body for females.
• Structure.
• Upper body: changes of bone structures into a more feminine form and a decrease of muscle mass and ability on the upper body for males; changes of bone structure into a more masculine form and an increase of muscle mass and ability on the upper body for females.
• Lower body: changes of bone structures into a more feminine form and a decrease of muscle mass and ability on the lower body for males; changes of bone structure into a more masculine form and an increase of muscle mass and ability on the lower body for females.

Depending on the kind of changes the body of a patient is undergoing, their symptoms can differ. The component of Sex is often linked with arousal and intense pleasure in the regions in which the changes occur. The component of Shape is linked with soreness, tingling and aching in the regions in which the changes occur. The component of Structure is linked with aches and sharp pains in the regions in which the changes occur. In all cases, the specific regions being either the upper body or the lower body. On average, a person who caught the disease undergoes changes in three different parts of the body, taking the components into account. As a consequence, they could, on a genetic level, be considered 50% male and 50% female. When the disease changes all six parts of the body, both upper and lower body sex, shape and structure, this would mean that a former male would become 100% female, and a former female would become 100% male as a consequence of catching HOST-D.

The severity of the changes to the body of a patient are very dependent to their hormonal balance. This fact means that teenagers are, as a consequence of hormonal imbalances during puberty or shortly after, more susceptible to undergoing physical changes than adults are. Although this might imply that adults are more immune to the sexually transmitted disease, though not in full, this does not mean they cannot be carriers of the disease, or better said, Hosts. Adult bodies typically undergo one to three changes, where prepubescent bodies can typically undergo a sum of changes between three and five, with outliers from all age brackets becoming the opposite sex in their entirety, or people being immune in full, a symptom more common among patients who are past the age of 50.

The rising population living with HOST-D became cause for medical experts and scientists to develop a cure for the disease. At the start, such a cure didn't exist yet. As time went on, different treatment methods became open to the public, but where HOST-D became treatable, it was not curable yet. Eventually, there might come a time where a cure is found and the disease disappears altogether.

Pick a time and place, anywhere from when and where the disease first emerges, to when the disease becomes so commonplace that more people have it than not, and existing cures have become commercialized, rather than a necessity. Society's view on the disease and its Hosts may vary as a consequence of this. Some people may wish to hide their unwanted changes, while others embrace it. Some might even open up more because of HOST-D. Their story starts here.