Brace yourself, as this is one of the weirdest and most bizarre computer virus-related stories that I have ever heard.

Back in 2012, a computer hacker used malware to infect innocent people's computers across Japan with a Trojan horse, and post death threats from them, giving the police no clue as to where he might really be located.

The hacker's campaign of terror included claims that public buildings would be attacked, threats against students at a Yokohama elementary school and educational establishments attended by Emperor Akhito's grandchildren, and menaces that there would be a mass-murder at a Tokyo comic-book convention.

"I will commit a massacre in Osaka’s streets. I will run over people, stab some at random and then kill myself."

On another occasion, a New York-bound Japanese Airlines jet was forced to turn back to Narita airport after an online bomb threat was made, costing the carrier over ¥9m.

It wasn't long before the Japanese police appeared to have found the culprit. Or perhaps culprits.

In fact, the police arrested four separate people, and allegedly managed to "extract" confessions from some of those whose computers had posted death threats to a popular messageboard.

However, the confessions were clearly unreliable (one wonders how the confessors were "encouraged" to make them), as the suspects had in fact had their computers infected by the hacker's malware, which had posted the death threats without their knowing.

It became clear to the police that they had made a colossal blunder, when the hacker - who went by the alias Oni Koroshi (Demon Killer) - continued to send taunting emails to the police force and local newspapers.

You can just imagine how embarrassing that must have been for the Japanese police, in what was becoming a high profile case.

Demon Killer was clearly bemused, sending a direct message to investigators:

"Thank you for playing with me."

The Japanese authorities weren't laughing however, and were sufficiently troubled by the threats and their failure to find the true culprit, that they announced their first ever bounty for information leading to the identification of the threat hacker responsible - a tidy ¥3m (which at the time, was approximately US $36,000).

And then things took a further bizarre twist.

Because the real hacker had a love for riddles, and was enjoying the game of cat-and-mouse he was playing with the media and Japan's bungling police force.

In a new series of five riddles, on New Year's Day 2013, the hacker sent media outlets "an invitation to a new game", that would lead to the "chance for a big scoop".

Once deciphered, the clues led investigators to the island of Enoshima, where a cat was said to be carrying a micro SD card in its pink collar. And on the card, according to the hacker, would be information related to the computer virus.

Amazingly, not only did some people go to the island to hunt for the hacker's cat, but it was actually found!

Here is a video of the cat being identified, and - yes - it's wearing a pink collar carrying a micro SD card.

Contained on the collar's SD card was a message criticising the police for once blaming the hacker for committing a crime that he alleged he wasn't involved in.

But here, the hacker's game of cat-and-mouse begins to unravel.

Because CCTV cameras on the island had captured images of Yusuke Katayama, an IT professional, spending quality time with the feline.

Searching Katayama's home, the police seized ten computers and discovered that many of them had TOR installed on them, a utility often used to prevent web activity from being tracked.

Katayama, it transpired, had been in trouble with the law before - having been found guilty of making online death threats against a music label in 2005, a crime which had earnt him 18 months behind bars.

Katayuma's lawyer Hiroshi Sato criticised the police for its failings in the case, and argued that perhaps Katayama's own PC had been infected by the same virus that had led the authorities to four other suspects.

But, as the BBC reports, it wasn't enough to convince the court, and 32--year-old Katayuma has this week been sentenced to eight years in jail.

Katayama, at his arrest

For now, the story is over, and it appears that the Japanese police have finally caught their man and put him away. After all, no more threats are being received.

What happened to the cat who featured at the centre of this bizarre case is, sadly, not documented.