For years we’ve had an understanding that Japanese TV is a little bonkers. Not only have we had glimpses of it with the crazy show Takeshi’s Castle, but audiences of a certain age will remember during the eighties Clive James on Television, that often showed clips of some of the more bizarre offerings from the land of the rising sun.

This fascinating and, some might say, disturbing documentary, follows the exploits of one show in particular, when it took the concept reality TV to a whole new level.

In 1998 a new TV show appeared on Japanese TV, Susunu! Denpa Shōnen that saw contestants take on crazy challenges. One of them was to audition a bunch of young men to take part in a competition to be filmed as part of the show, with the catch being that none of them were told what was involved.

One of the young men auditioning was comedian Tomoaki Hamatsu, who although wanted to be famous, had no idea what he was letting himself in for when he ‘won’ the audition.

His prize was to be stripped naked in a bare apartment in the city, surrounded by an array of magazines, which he had to enter competitions that they run, to survive. He would complete the challenge once he had won the equivalent of 1 million Yen (£6,300/$8,000) in prizes.

And although he was aware he was being filmed, he was told that most of it wouldn’t be used, unaware that he was being seen every week on the show, by huge audiences, before finally being streamed live on the internet 24/7 without his knowledge.

British director Clair Titley’s documentary is an astonishing look at how far the boundaries of reality TV can be pushed.

As fascinating a watch as it is, there’s also no denying how disturbing the premise is and the undeniable toll it takes both physically and mentally on the contestant in question.

Titley has a lot of time with Hamatsu, better known by the nickname Nasubi, and it’s evident now from his body language and replies that the whole ordeal made a tremendous impact on him, which you suspect he isn’t full over even now.

It raises some interesting points, such as how far is too far, in order to achieve massive ratings, which the show did, managing to draw in over 15 million viewers every week, all of whom were keen to observe how Nasubi was doing.

It is the stuff of nightmares, especially when you consider how long Nasubi was subjected to what it tantamount to televised torture, with the show running well over a year.

The film loses its focus towards the end, getting caught up in Nasubi’s drive to climb mountains, which if nothing else, gets him out and about in the fresh air.

It should also be remembered that this took place before the release of The Truman Show as well as the explosion of Big Brother on our screens.

Its premise is certainly one that sounds like it would make an intriguing horror film, but of course the real horror comes from the fact that this was reality, and really not that long ago either.

It should be said that Nasubi was never locked in the apartment, so could leave under his own steam at any time. However, the psychological damage it must have inflicted on him certainly shows signs of Stockholm Syndrome, so the reality is that he had little by way of free will by the end of it.

But as shocking as it all is – even more so to see a nation gripped every week by his public incarceration – you are left with the sense that it’s likely that the boundaries of reality TV are more than likely to be pushed even further, somewhere down the line, in what will be an even more brutal contest.