Japanese reality show contestant was naked for a year — and had no idea 30 million people were watching

Tomoaki “Nasubi” Hamatsu wanted to be a famous comedian — but he did not want to become an international laughingstock.

Yet that’s exactly what happened when he unwittingly appeared naked for weeks on end before some 30 million Japanese TV viewers.

The brutal experience is revealed in the new Hulu documentary, “The Contestant,” out Thursday.

In 1999, the then 24-year-old thought he was auditioning for a “showbiz-related job” on a new TV series called “Susunu! Denpa Shonen,” which translates to “Do Not Proceed! Crazy Youth.”

It was the era of Japan’s outrageous challenge shows, which found contestants shutting their eyes and biting into mystery objects — maybe it was a bonbon; maybe it was a shoe — or trying to climb slippery steps, or picking a potential girlfriend based only on a lineup of bare butts.

The point of “Denpa Shonen” was to put participants, often young comedians willing to do almost anything to get famous, in extreme situations.

But Nasubi didn’t know what he was signing up for when Toshio Tsuchiya, known as the “King of Reality Television,” showed him to a windowless studio apartment in Tokyo.

It contained a desk with postcards, magazines and a diary, in which Nasubi was told to chronicle his experiences in the room.

“Tsuchiya was a very famous producer,” Nasubi told The Post. “I felt honored to have gotten picked. He, to me, was like a person in the sky. I had admiration for him. But that changed. He became evil. My respect eventually turned to anger.”

His doubts began when Tsuchiya ordered him to strip.

“I did not want to be naked,” Nasubi said. “I told him that a million times. But he insisted. I did it. Then I told him that I did not what to be broadcasted.”

Nasubi was assured that he would not be.

But, unbeknownst to him, hidden cameras were already rolling.

He was told by producers that, in order to complete the challenge, he could not leave the room until he won prizes, via magazine sweepstakes, totaling 1 million yen (then the equivalent of $8,000; now, around $15,000).

And he would need those prizes to survive.

Thus began Nasubi’s run as the unwitting star of “My Life in Prizes.”

Lest he be reported missing, Nasubi’s parents were called and told that he was featured in a TV show.

“They were made to believe that I wanted to do it,” said Nasubi. “In reality, this was kind of like a kidnapping call. My family did not know what I was going through.”

Soon enough, though, some 17 million people in Japan knew — as his challenge was broadcast every Sunday night on the Nippon Television network.

Naked on the screen, with an eggplant emoji digitally added to cover his penis for TV viewers, he entered as many as 400 contests a day in order to win survival tools and even basic comforts.

Early on, Nasubi won a bag of rice — but had no way to cook it.

His hair grew unruly.

Days turned to weeks, and he hopped around the room like a monkey.

Prizes rolled in: Cooked meat, potato chips, dog food (the canned food grossed him out; he savored the dry stuff), lady’s underwear, a live lobster.

It took 10 months of wiping himself with his hands before he won toilet paper.

Twelve cartons of high-fiber jelly, he said in the doc, “wasn’t enough to fill me up but it was enough to keep me alive.”

Nasubi’s mental state was not much better.

“I would say that he had a nervous breakdown on the show or else he came close,” Clair Titley, director of the documentary, told The Post. “He was pushed to the mental limit.”

The premise?

According to Tsuchiya: “We are trying to show the most primitive form of a human being.”

Still, Nasubi could have walked out — albeit, naked — at any time.

“I thought about escaping so many times,” he said. “But I got into a mental syndrome. I had the attitude that that this was something I decided to do, so I had to keep doing it.”

When some fans speculated that he lived outside the room and entered only for filming, an incensed Tsuchiya ran started running a 24/7 online feed.

Smirking in the documentary, he said, “I am the devil.”

On day 333 of the torture test, Nasubi won a bag of rice, valued at 764 yen.

It took him to 1 million.

Tsuchiya woke him up by shooting party poppers on his naked body.

Told that he won — and believing it was over — Nasubi raised his toothpick-thin arms in victory.

Dressed and blindfolded, he was transported to Seoul, Korea.

After being treated to barbecue and a pot of kimchi, he was led to another room and told to strip for another round of the monstrous game.

At first he resisted.

But after three hours of hectoring from the producer — who told him, “If you can hold on just a little longer, you can grow another level as a human being” — Nasubi agreed.

But, he admits now, “I did think about committing suicide.”

After completing his mission in Seoul — all told, a 15-month challenge — Nasubi was blindfolded and transported to yet another small room.

Again, he stripped.

Suddenly, all four walls of the room collapsed outward.

He found himself on a TV studio sound stage, before a frantic audience.

The truth was revealed: Nasubi was an unwitting TV star.

“I had no idea what was going on,” he said. “It took me a while to realize what had happened. My mind was blank.”

For everything he went through on the show, Nasubi received only $8,000.

His diaries were published and became bestsellers — but, he says, he saw none of the money.

The last couple of decades have been strange for Nasubi.

“So many girls came to me,” he said. “But they stared at me like a panda in a zoo. Instead of being attracted to me as a guy, they were attracted to me like an animal. Put it this way, I’m not married.”

His family eventually forgave him.

“They thought of me as an idiot,” he admitted. “My one promise to my mother, when I decided to be a comedian, was that I would never be [publicly] naked. I broke it. My family told me to not be so silly again.”

He now makes his living through small-time stage acting, promotional appearances and occasional TV spots.

Now a successful comedian and actor, Nasubi does not hold much of a grudge against Tsuchiya: “It’s not like I get along well with him. But I have a connection.”

Asked if he regrets the experience Nasubi hesitates. “It’s hard to give you an answer,” he said. “When I die, I will think about it, and tell you then.”