A man was arrested in Japan on Saturday after a prank – shooting compressed air deep into a workmate’s rear end – ended in tragedy.

But the crime, while bizarre, is far from unique in Japan, where a common childhood practice may explain a succession of adult deaths and injuries in recent years – all related to anal assaults with air compressors.

The Ibaraki Prefecture Ryugasaki Police on Saturday arrested 34-year-old Yoshiyuki Yoshida for accidentally killing his 46-year-old co-worker Akio Ishimaru.

According to the police and other sources, Yoshida and the victim both worked at an industrial equipment manufacturing plant in Ibaraki Tsukuba City. At round 5pm on July 13, during a break, the two were apparently clowning around when Yoshida jokingly took an air compressor on the site and poked Ishimaru between the buttocks with it, injecting a blast of lethal wind deep into the victim’s body.

A few minutes later, Ishimaru begin to complain that he felt unwell. A colleague called emergency services, which dispatched an ambulance to the scene. Although Ishimaru was swiftly transported to hospital, he did not survive the indignity he had suffered.

Yoshida has confessed, and now faces charges of assault resulting in death. “I just did it as a prank,” Yoshida told police. “I didn’t think he could possibly die from that.”

According to a spokesman at the Ryugasaki Police Department, “It was a tragic accident but not the first of its kind. The air compressor was pushed up against the anus, over clothing, not directly into the cavity, and the release of the air into the body probably damaged the lungs, causing death. We are waiting for the results of an autopsy, which is still being scheduled.”

A record of indignities

Japan is a country remarkably free of guns and gun deaths – even the yakuza avoid them – but in recent years has been plagued by an unlikely lethal weapon: the air compressor. Yesterday’s death is, in fact, just one of several incidents related to air being forcibly blasted up backsides.

On December 16, 2017, two men working at an industrial waste disposal factory, in Saitama Prefecture accidentally killed their co-worker. The three men were using the air compressor to blow dirt and grime off of their uniforms, when they pranked their 44-year-old colleague by poking him in the rear with the air compressor. Both co-workers were arrested on charges of assault resulting in death.

In fact, the year had started with an ill wind. On January 1, a 28-year-old student in Kyoto died after being prodded by his friend, between the buttocks, with an air-duster gun.

Even the armed forces are not immune. In 2013, members of Japan’s Self Defense Forces pranked each other with air compressors, resulting in serious wounds and hospital visits. Fortunately, there were no fatalities from the soldiers’ rear assaults.

The culprit: childhood finger enema?

While it might be considered common sense not to attack a friend’s bodily cavity with an air compressor, there are cultural precedents for similarly invasive practices in Japan. The island nation is home to a dastardly childrens’ prank known as “kancho.”

Kancho is a performed by cheeky Japanese kids. In it, the child clasp the fingers of both hands together to form an imaginary gun with which they poke their unsuspecting victim in the anus, while yelling: ”Kan-CHO!”

The word “kancho” comes from the Japanese word for enema.

The practice of assaulting co-workers’ rear ends with air compressors appears, essentially, to be a dangerously equipped variation of this well-known and rude, but often overlooked, childhood prank.