Once described as a geek who stuffed himself with snacks in front of his computer, Mark Karpeles rose to head a firm that once claimed to handle 80 percent of the world's bitcoin transactions.
But his lavish Tokyo lifestyle came to an abrupt end when prosecutors charged him with data falsification and creaming off millions of dollars of customer deposits from his cryptocurrency exchange MtGox.
On Friday, he was found guilty of the data faking charge but acquitted of embezzlement, resulting in a two-and-a-half-year sentence, suspended for four years.
RISE AND FALL
In many ways, the trajectory of the Frenchman, now 33, mirrors the volatile rise and fall of the bitcoin currency itself, which had soared to around $20,000 per unit before a head-spinning slump.
According to his mother, Karpeles, whose real first name is Robert, had few friends at school, as he was "unable to find a buddy who could talk like he could about IT and quantum physics".
The "only thing that interested" her "talented" son was computer science, according to his mother, speaking in a 2017 documentary.
Karpeles himself admitted to French television that he would spend entire days in front of the computer screen without the slightest bit of physical activity.
Entering the professional world, he quickly found himself at odds with his French company Linux Cyberjoueurs, which found irregularities in its data and pointed the finger at Karpeles.
The firm brought the case to the authorities and in 2010, he received a year's suspended sentence in absentia in France for "fraudulent access of an automated data processing system" and "fraudulent altering of data".
But by this time, Karpeles was in Japan, which he had visited several years previously and found the people and culture to his liking.
Once in Japan, he founded his own company, called Tibanne – after his cat.
But his life really changed the day a customer asked if he could pay in bitcoin – a new virtual currency that was just taking its own baby steps.
The virtual currency appealed to the computer whiz and he began to delve into the technical and IT aspects of the new trend.
By 2011, he had bought his own cryptocurrency exchange MtGox, the name inspired by a "magic" card-swapping platform beloved by Japanese "otaku" or "geeks" called "Magic: The Gathering Online eXchange."
This grew rapidly until, at the height of its powers, it claimed to control 80 percent of all global bitcoin transactions.
"He was excited by the money that could be generated on this exchange market," one of his associates told a television documentary under the cover of anonymity.
And Karpeles enjoyed the trappings – reportedly lodging in an $11,000-per-month luxury pad with a king-sized bed worth tens of thousands of dollars.
He married a Japanese woman and became a father but everything came crashing down in 2014, when MtGox suffered what Karpeles said was a "massive" hack attack and lost around 850,000 bitcoins, worth just under half a billion dollars at that time.
He had tried to take the traditional path of bowing deeply and apologising profusely – in Japanese – for the losses.
But this earned him only mockery online and did not deter the authorities.
He was arrested in August 2015 and spent a year in Japanese detention after being re-arrested several times, as is possible under the legal system in Japan.
When he was finally released on bail, he had lost a huge amount of weight and at his first high-profile hearing offered up a clean-cut image.
Since then, Karpeles has been active on social media but has largely avoided commenting on his case in detail as he awaited the court's verdict.