There’s a tendency in some societies to associate a period of history with the crimes that occurred therein. This is why we use expressions such as “crime of the century.”

And Japan? Crime certainly figures prominently in a 264-page mook published by Bungeishunju titled “Heisei 1989-2019 wo Yomitoku 51 no Jiken” (“Fifty-one Incidents for Reading and Understanding the Heisei Era”), with 14 of the 51 incidents, or 27.4 percent, involving violations of the criminal code.

Meanwhile, another mook recently published by Yosensha titled “Gekido no Heisei-shi” (“The Turbulent History of Heisei”) devotes eight pages to crime and four more exclusively to the yakuza, whose full-fledged membership at the end of 2016, author Atsushi Mizoguchi reports, had declined precipitously to 18,100 — with another 20,900 counted as “apprentice gangsters.”

Could any types or patterns of crimes be described as Heisei-specific? Possibly. In Shukan Asahi (Jan. 9, 2018), sociologist Shinji Miyadai described the era of Heisei as “a morass of paranoia and megalomania.” Others had already observed a growing trend toward so-called “delusionary crimes” — which are not committed for the usual motives of monetary gain, hatred or revenge, but to satisfy some demented urge, and even for pleasure.

In addition to assaults by random slashers, these include forms of erotomania such as stalking, voyeurism and theft of women’s underwear from clotheslines. Like other relatively “new” types of crimes, such as domestic violence, it’s difficult to ascertain as to whether the number of cases actually increased, or if they just reflected enforcement of new laws designed to play catch-up with an already existing situation.

The half decade-long economic “bubble” that began in 1986 and its spectacular collapse was blamed for numerous cracks and distortions in society, such as having helped to spawn the doomsday cult known as Aum Shinrikyo. Begun as a school teaching yoga and meditation, Aum’s partially blind “guru,” Chizuo Matsumoto — who was hanged in July last year along with a dozen other followers after two decades on death row — indoctrinated (or coerced) thousands of young adherents who lived austerely in communal “satyams,” turning over all their possessions and earnings to the cult.

Aum also attracted people with advanced degrees in chemistry, who turned their skills to producing sarin, a toxic nerve gas, in a secret laboratory near Mount Fuji. After testing it one summer night in the city of Matsumoto in 1994 and leaving behind seven corpses, the team of mad scientists slinked back to their lab to prepare for a bigger target. Believed to have been tipped off that a police raid was in the works, the cult struck first, releasing nerve gas on Tokyo subway commuters on the morning of March 20, 1995 — killing 13 and sickening thousands.

As the year 2000 approached, the weirder and more bizarre crimes became, leading some to attribute them to a seikimatsu gensho (the fin de siecle phenomenon) — as if humans were becoming infected by an organic version of the much-feared Y2K millennium bug. In spring of 1997, the city of Kobe was terrorized for two months following the murder of an 11-year-old boy, whose decapitated head was placed outside the gate of a junior high school. Thrust into his mouth was a handwritten letter, signed “Seito Sakakibara,” challenging the police to “begin the game.”

When police announced an arrest two months later, the suspect turned out to be a 14-year-old boy, and to describe the nation’s reaction as “shocked” was an understatement. “Youth A,” as the perpetrator was referred to in the media, would spend six years and five months in custody, during which he received psychological counseling. Although he has never appeared in public, he published a 294-page autobiographical memoir in 2015 titled “Zekka” (“Song of Desperation”).

Unsolved major cases continue to haunt Japanese society. Just over 18 years have passed since businessman Mikio Miyazawa, his wife and their two children were murdered in their home in Tokyo’s Setagaya Ward on the night of Dec. 30, 2000.

In a 12-page article appearing in the New Year’s edition of the monthly magazine Bungei Shunju, author Iku Aso professes to offer “new facts” concerning the killings. As one possible scenario. Aso suggests the murders might have been committed by a foreign intelligence operative (possibly from North Korea) as a “test,” to see if he could be relied upon for future assignments. The killer, Aso claims, would not have been overly cautious about leaving behind fingerprints and his DNA had he known he’d be departing Japan within a matter of hours.

Unfortunately, these kind of creative deconstructions don’t qualify as legally admissive evidence, so until the police announce they have caught their man, Aso’s interpretation remains in the realm of speculation. The statute of limitations for murder was finally abolished by the 2010 revision to the Code of Criminal Procedure, and the Metropolitan Police Department still maintains a task force of investigators, treating the Miyazawa killings as an open case.

While some see proactive attempts at crime prevention like the installation of ubiquitous security cameras — some with facial recognition capability — as evidence of Japan’s continuing evolution into a kanri shakai (regulated society), law enforcement can claim some successes, particularly fewer crimes committed with guns. Ownership of handguns is banned outright in Japan and sales of shotguns and hunting rifles, as well ammunition, are strictly regulated. For the previous half-decade, murders committed by firearms have been held to a single digit per year (with only three in all of 2017).

Big in Japan is a weekly column that focuses on issues being discussed by domestic media organizations.