I suppose most of us have experienced the mildly perverse pleasure of a full-bladder and its eventual release, or felt a gently sadistic joy at witnessing a loved one's discomfort when they desperately want to piss in a public space, but are denied the opportunity to do so (the thought that they just might not make it home amusing and arousing in equal measure).
But only the Japanese have given this variant form of urolagnia a specific name - omorashi - and have not only developed it as αn idea within the pornographic imagination, but built a fetishistic subculture upon it, thereby allowing like-minded individuals who delight in bladder desperation and panty wetting to exchange stories and images and to meet up if so desired.
It should be noted, however, that for most devotees of omorashi an exchange of bodily fluids is not desired; they neither wish to piss on others, nor be pissed on by them. Nor do they want to see naked organs in close-up action, or hope that things might develop in an overtly sexual manner.
For the obsession is ultimately with clothed incontinence and omorashi videos tend to focus on the garments worn by the participants; these invariably include schoolgirl uniforms, but films with women dressed as business professionals - looking dignified and in control, before shamefully succumbing to the need to urinate - are also very popular with certain male viewers.
Now, whilst we might legitimately have concerns with some of the dubious sexual politics played out within the world of omorashi, it is, I think, relatively harmless and is frequently looked down on as too tame by hardcore fetishists for whom watersports involves far more edgy and unsettling elements.
However, under current UK legislation I wouldn't be at all surprised to find that even omorashi is categorised as a form of extreme pornography and that peeing your pants has thus been made into a criminal offence!
Note: thanks to political writer and researcher - and defender of civil liberties - Nick Cowen, for his kind advice on this post.