TOKYO -- A string of robberies has been occurring in the Japanese capital and surrounding environs including Saitama Prefecture. The perpetrators have been committing their crimes in a crudely conspicuous way, breaking windows to enter private homes even while the people living there are inside, then tying them up. The Mainichi Shimbun asked a security consultant how residents can avoid becoming victims and stay safe.

Possibly the work of 'anonymous and fluid' crime group

In the early hours of Oct. 1, four men allegedly smashed the window of a side door at a home in Tokorozawa, Saitama Prefecture, and tied up the married couple in their 80s living there. The assailants made off with around 80,000 yen (some $540) in cash, among other things. Saitama Prefectural Police arrested three men nearby on suspicion of robbery and inflicting injury. Three of the men reportedly had not met previously, and have each explained that they applied for a "shady part-time job."

The day before, a woman in her 60s was tied up after robbers smashed the glass of a side door window at her home in the Tokyo suburban city of Kokubunji.

Saitama Prefectural Police began a joint investigation with Tokyo's Metropolitan Police Department (MPD). Because of similarities in the techniques used to enter the homes, their use of adhesive tape and other factors, the incidents are believed to have potentially been directed by the same leader, who hired the perpetrators over social media to become a so-called "anonymous and fluid" crime group.

Old houses on the edge of the city targeted

Since August, no fewer than seven homes and businesses have been hit by robberies in the wider Kanto region surrounding metropolitan Tokyo. "Crime prevention adviser" security consultant Mika Kyoshi says that countermeasures are needed nationwide, not just in the area hit by the recent spate of offences.

"If the perpetrators are hired to carry out the crimes as 'shady part-time jobs,' they may be repeated all over the country unless the person directing the robberies is arrested," said Kyoshi.

What kinds of homes are susceptible? Kyoshi said, "Old detached houses in the suburbs appear to be the targets. This may be because the criminals believe that elderly people who keep cash at home for living expenses are more likely to live there."

Wire-reinforced glass no protection against break-ins

In both aforementioned robberies, the culprits entered the home by smashing side-door windows. "Windows in blind spots not easily visible from the surroundings, such as kitchen doors or rear bathrooms, tend to be targeted," Kyoshi pointed out.

According to the two investigating police forces, the side doors on both homes had wire-reinforced glass. "Although this has the disaster prevention effect of preventing glass from scattering in a fire or earthquake, it is quiet when broken and the mesh breaks as if a hole is punched in it, so it's not helpful for crime prevention," Kyoshi said. Instead, she said it is effective to install multiple auxiliary locks or apply anti-shatter film to the glass, among other steps.

Regarding anti-shatter film, Kyoshi advised, "To ensure a level that can withstand an attack for five minutes or longer, it's desirable to have a film with a thickness of at least 350 micrometers, or 0.35 millimeters."

The Association of Japan Window Film Manufacturers also considers 0.35 mm as a requirement for products to be deemed a "building component with high security performance" by a public-private council made up of the National Police Agency, private organizations and others which carries out endurance testing.

Kyoshi advises, "In taking countermeasures, first keep in mind the 'four basic elements that criminals don't like,'" which are sound, light, time and visibility to others. Example methods include installing alarms to sound when glass is broken, motion-detecting lights, security cameras, and auxiliary locks to increase the amount of time needed for a break-in.

What if robbers invade one's home, despite these efforts? Kyoshi urged, "If possible, run outside and call for help. Otherwise, run to a room that can be locked, such as a bathroom or bedroom, and call 110 (the police emergency number in Japan). If confronted, put your life first."

(Japanese original by Ei Okada, Digital News Group)