Yoshinori Ishimi could hear a high-pitched whine coming from the apartment in Nerima Ward, Tokyo, he was about to enter. When he went inside, he saw black “mini-twister” clouds of flies.

The last tenant had been a 60-year-old divorced man whose body was not found until a month after he had died.

“Every time I encounter such scenes, I hesitate to step inside. But someone has to clean up these flats . . . and be professional about it,” said Ishimi of Anshin Net, a cleaning service that is part of R-Cube Co. in Ota Ward, Tokyo.

The Nerima man’s case was not unique, and such unnoticed departures are only expected to increase.

According to a report by the National Institute of Population and Social Security Research, the number of single-person households is expected to rise from 14.46 million in 2005 to 18.24 million in 2030, or nearly 40 percent of all households.

With the growing number of single households in this graying nation, businesses specializing in dealing in what has been dubbed “lonely death” have become a fixture.

Anshin Net is one such example.

Founded in 2004, the company handles about 450 requests a year, about half of them dealing with cleaning out dwellings after the occupant has died.

The requests generally come from close relatives. But when people die alone and their corpses are not discovered for weeks or even months — the requests may also come from landlords, as well as more distant kin, because many people die childless and without a partner, Ishimi said.

“We receive about four to eight requests a month asking us to clean dwellings where the residents were found a week, a month, or, in extreme cases, a year after they passed away,” Ishimi said.

Police process solitary deaths by carrying out autopsies and, if relatives can’t be traced, municipalities cremate the body and inter the ashes in a shared grave, Ishimi said.

Ishimi and other specialist cleaners come in afterward and make dwellings clean again.

Although no figures are available, with the increasing media coverage about people dying lonely deaths, both the number of people engaged in this business and job requests have surged in the past two or three years, said Atsushi Takaesu, 38, an Okinawan who has run a special cleaning business in Kanagawa Prefecture since 2003.

“I had only about 10 cases a year about seven years ago. But this year, the number is likely to surpass 400. I received about 40 requests this June alone,” said Takaesu, who recently published “Jiken Genba Seisonin ga Iku (“Here Comes a Crime Scene Cleaner”), a nonfiction book on his specialty of cleaning housing where people died lonely deaths, including suicides.

Takaesu said he is proud of his job but admits that at times it is heart-wrenching.

Pointing to a picture of a bathtub one-third full of a dark reddish liquid, Takaesu explained: “This is not ramen. This is a dead lady’s body fluid and skin. I actually had to step into the bath to clean it.”

Apart from the flies, maggots and pupae, crawling, sticking to windows and flying around, there is the hair of the dead, looking like a wig.

Also, bodily fluids and blood soak into tatami mats, and there is the stench of death that many in the business find difficult to totally remove, according to Takaesu.

“It is hard to pick up someone’s hair with my own hands, but if you ask me whether I can do it, I can. But the appreciation I get after I clean up those rooms, totally removing the lingering smell of death, is the biggest thing that keeps me going,” he said.

Ishimi of Anshin Net said people who die alone often share the same circumstances, and he strongly believes many can avoid this fate by changing their lifestyles.

“Many were men in their 50s or 60s, divorced, and with no job. They had not been in contact with their friends or families and they often were diabetic,” Ishimi said, adding that when he goes inside their dwellings he often finds the curtains drawn and piles of empty food boxes from convenience stores, cans or bottles of alcohol, and insulin vials.

“It’s sad. And to be honest with you, I ask them (the deceased), ‘Why?’ Because (in many cases) if they had changed their lifestyle, they could have avoided dying (in the way they did). They shut out the sunlight and fresh air with curtains, and isolated themselves from everyone,” Ishimi said.

After seeing so many residences long after the occupant’s death, Anshin Net is now shifting its focus on what it calls “welfare cleaning.”

About half of the requests the company receives today are from care managers, helpers or sometimes municipalities asking for help cleaning the dwellings of elderly people who live alone and have huge garbage accumulations.

These people call first because they can’t enter the elderly person’s house unless the waste is removed, or, in some cases, following complaints made to municipalities from neighbors, Ishimi noted.

“In recent years, the number of elderly who live alone buried under a mountain of garbage has surged. Some have dementia and some are physically unable to take out the garbage. It is these people who are the ones most likely to die alone,” Ishimi said.

“We want to minimize cases in which elderly people die alone. I believe cleaning their housing will act as a deterrence.”