For more than a decade Kazuhide Inoue has played an understated part in protecting the morals of adolescents in Fukuoka. Several times a year, the 73-year-old visits eight white “post boxes” installed in the city in western Japan, turns a key and empties their contents. On a recent visit, his haul totalled 16 books and 81 DVDs in a single day.

But the boxes are not drop-off points for rental shop customers: they are for the exclusive use of people – almost always men – who want to discreetly dispose of unwanted pornographic material that, if kept at home, could fall into the hands of unsuspecting children.

“Before the white boxes were installed, this stuff littered the streets,” Inoue told the Kyodo news agency. Street bins are not as numerous in Japan because people usually take their litter home. Rubbish bins practically disappeared from streets in Japan after the 1995 sarin gas attack on the Tokyo subway.

But now, the avalanche of digital pornography available on smartphones is rendering the boxes obsolete.

The number of shiroposuto, recognisable by their colour and messages promoting children’s wellbeing has fallen dramatically over the past decade. Although no official count exists, the white boxes – joined later by less conspicuous steel receptacles – are quickly becoming a cultural curio.

Last year, officials in Nagasaki closed several white post boxes on a trial basis after the number of collected items plummeted from between 5,000 and 6,000 a year in the first decade of the millennium to around 2,000 today.

‘Men of all ages come to get rid of their stuff’

Shiroposuto – white post boxes – first appeared in the city of Amagasaki in 1963, following a campaign by local mothers’ groups determined to tackle the corrupting influence of the postwar explosion in pornographic books and magazines.

Tokyo didn’t get its first porn drop box until 1966, but within three years the capital had an estimated 500, as the tactful disposal of such material spread beyond its western Japan base.

“The campaign to install them was led by mothers who didn’t want their children exposed to anything harmful, including pornographic books and magazines,” says Yuko Obi, an associate professor of sociology at Tokyo Keizai University who has researched the history of shiroposuto.

Most are installed outside railways stations, where men dispose of redundant material, often under the cover of darkness to avoid being spotted by a friend, colleague or neighbour.

“At night, when the streets are less crowded, men of all ages come to get rid of their stuff,” a taxi driver in Fukuoka told Kyodo.

Regular hauls of books, magazines and DVDs in some locations suggest they have not quite outlived their usefulness. The city of Fukui installed two boxes as recently as 2018, while some need emptying as frequently as once every three months.

It isn’t clear how many of the post boxes remain. There is thought to be just one in the Tokyo metropolis, in the western city of Mitaka, but Obi says they are in greater demand in regional cities, particularly among older men who are still attached to pornography in its analogue form and want to offload their collections discreetly.

With the advent of online porn, shiroposuto have become more akin to regular rubbish bins, their role in protecting children from harmful material now less of a factor. “They were a success when they first appeared in the 1960s, but Japanese society has changed, and the way people consume media has been transformed,” Obi said.

“Back then, there was a lot of pornographic material in circulation, and campaigners did a good job of raising awareness about shiroposuto, but in the age of digital media it is impossible to hide harmful material.”

The boxes are the latest victim of Japan’s long campaign to rid public spaces of obscene or risqué images, particularly in the run-up to large international events.

Major convenience store chains announced they would end sales of pornographic material in the run-up to the 2019 Rugby World Cup and the Tokyo Olympics two years later, citing concerns the material could tarnish the country’s image amid an expected surge in foreign visitors.

Vending machines that appeared in the 1970s selling pornographic magazines have also been targeted, although it is possible to find rare survivors of the cull in remote towns.

Japan’s ageing population could sustain porn repositories for a while yet, but Obi believes their days are numbered, partly due to the cost of maintaining them.

“They get old and rusty and have to be repaired, but not everyone wants taxpayers’ money to be spent on that,” she says. “And they have to be emptied by a local board of education officials, sometimes accompanied by a police officer. “That’s why I think the number of shiroposuto will continue to decline.”