This world is much like the “normal” world.
If one was to walk down the street of any town in the world one would find it almost the same, the only thing that would stand out was that it seemed like everyone from the age of 22 to 30 carried a melee weapon of some kind.
They carry those weapons be it a sword, the most common or an ax, mace, quarterstaff or something else because in this world people do not date, they duel.
All duels are done with melee weapons, no range weapons of any kind outside of a whip or other melee weapons using chains are allowed. Guns, bows and arrows and the like are not allowed.
When a duel happens, it is for their very life for if they lose the winner can claim them as their master or mistress. And once they lose the winner can also transform them into whatever they find attractive.
While there are some limits by law of what a person who loses a duel can be turned into most transformations are accepted. Only real limits are making someone totally an animal, regression below the age of 21 or above 30 and making someone an inanimate objects unable to make an attempt to regain their freedom.
A loser can have their only small parts of their bodies changed or everything from height, weight and sex can be changed by the whims of those who win the duel. Almost always their sexual desires are changed to match the wants of the winner.
Once a duel it loss a person can not regain their freedom unless the person who won their duel losses a duel themselves. If that happens, they are given a chance to fight their new owner in a duel for their freedom, if they win they get their freedom, if they lose their new master can transform them.
The only other ways for a person to regain their freedom is if they win another duel with their master, they get 3 chances but they can not challenge their master until a year had passed but after 3 failed attempts they lose that right.
The only other way is if a master releases them and let them go which can happen but is rare, because harems are not only allowed but common.
In this way it is possible for a person extremely skilled in their weapon to have harems of those people they defeated. A woman can have a harem just as much as a man.
While it isn’t official it is common that if a person is challenged and wins, if they have no interest in a person they can release a person without transforming them.
A person can turn down a duel, however a person can only turn down 9 duels a year max and a person can challenge the same person more than once a year. Once a person reaches 31, they can not be challenged to duel anymore and are free from being transformed or are stuck in their "new" bodies.
That is the world.