'Unbirth' Slime Girls

In this setting, a large portion of the population are slime girls.

Slime girls are women who rather than being made out of flesh, are made out of gelatinous, semi-liquid goop. Because of this, they are able to change their shapes from their default of beautiful voluptuous women.

In order to reproduce, a slime girl must 'marry' a female human. This involves taking the human entirely inside of their body. Once their 'wife' is inside them, the slime girl's liquid body will invade every orifice of the human, filling up every imaginable part of the woman's body. The human is then permanently trapped inside the slime girl. The part of the slime girl extending into her 'wife's' body provides all nutrition for the human, and the part of the slime girl extending into her wife's nostrils and lungs will provide oxygen. The part of the slime girl extending into her wife's ears allow the wife to communicate telepathically with the slime girl, though nobody other than the slime girl will ever communicate with the human ever again.

Once the wife is taken inside, the slime girl's body will pump into the wife's womb, filling her up to bloating. From there, the slime will insure that the wife is constantly pregnant with new slime girls. This means that, unless the slime girl deliberately halts the process, their 'wife' is being fucked at all times.

Slime girls are immortal, and any woman they take into their body will be rendered immortal as well, so their situation will last forever.

Once a human woman is taken into a slime girl's body, regardless of that human's identity or prior status, they are considered legally married to the slime girl and the slime girl can do whatever they want to them. The only caveat is that they the human must first consent to being taken into the slime girl's body. Because a human taken in this way can no longer communicate with anyone except the slime girl who took them, however, some slime girls will take a human woman they are attracted to into themselves by force, and claim that the woman agreed to it, as it will be difficult to prove that this was not the case. Other slime girls will secretly seduce human women to get them to agree to this. Many slime girls prioritize smaller women, as smaller women will be less difficult to fit inside their bodies.

The body of a woman inside a slime girl remains unchanging, forever.

A slime girl's body is mostly transparent, meaning that a human inside them is fully visible at all times.

Slime Girls can only marry humans, and do not marry other slime girls.

Slime Girls sleep in special tubs designed for slimegirls to revert to a formless state without having to worry about their bodies flowing elsewhere in their sleep.

When a human is taken into a slime girl's body, the human's body remains perfectly intact and does not melt.