A cryptocurrency built for watching live-streaming porn is turning out to be a buzzkill.

Four investors in the digital currency, called Fantasy Market, claimed last week that its shadowy CEO disappeared with their money — and has not refunded all their investment despite repeated requests.

The alleged inability of investors to trade out of the Fantasy Market tokens, or FMtokens, could stand as a warning to all investors in the red-hot cryptocoin market.

Jonathan Lucas, the brains behind FMtokens, was aiming to raise as much as $25 million last year, according to Lucas’ white paper — the investment plan circulated among investors.

FMtokens would be used to pay for viewing live-streaming porn, the paper said.

Cryptocurrencies like bitcoin, ethereum and ripple, with their values soaring, are among the buzziest investments on Wall Street.

FMtokens, like other initial coin offerings, or ICOs, usually have limited use — unlike cryptocurrencies — and often use the technology supporting ethereum.

Cryptotokens are also wildly popular investment assets. They are thinly regulated and are subject to wild swings in valuation.

Because of their volatility and lack of regulation, Securities and Exchange Commission Chairman Jay Clayton in December voiced his concern about Main Street investors jumping into ICOs with dreams of making a fortune.

Clayton’s statement came too late for the irate FMtoken investors.

The venture flamed out in November after The Post questioned Lucas for about an hour on how his ICO would work and about statements he made in the white paper.

“Jonathan Lucas (most likely an alias) has scammed us and run off with the cryptocurrency,” one irate investor fumed to The Post, more than two months after investing in Fantasy Market.

It’s unclear how close Lucas got to his $25 million fundraising goal. He told a reporter in November he had raised less than $2 million.

But he boasted in September in private chats seen by The Post to being just 13 percent away from raising $5 million — which translates to about $4.4 million.

Lucas, who has not been charged with any wrongdoing, didn’t return a request for comment.

The company, on its site on Sunday, appeared to be trying to get money back to investors — asking out-of-pocket investors to contact them “in the next 90 days.”

One investor who got a refund is still unhappy.

“[Recently] I wrote threatening to file police and FBI reports,” a second aggrieved investor told The Post. “Within hours they refunded me ethereum with a dollar amount equal to what I had contributed in early September, but since the coin has more than tripled in value since then, they kept the rest of my contribution, essentially stealing quite a lot of money from me.”

Investors had to buy FMtokens with ethereum, whose value has risen 160 percent in the last month.

A third investor claimed that Lucas appears to be actively trading on cryptocurrency exchanges.

“I’m not in the business of scamming people, or again, I wouldn’t have used my real name for the project,” Lucas wrote in a Nov. 14 chat.