The Toyama No. 5 apartment block is quiet at midday -- laundry flapping from balconies, old people taking an after-lunch stroll. But the building and its nearby park may be sitting on a gruesome World War II secret.
A wartime nurse has broken more than 60 years of silence to reveal her part in burying dozens, perhaps hundreds, of bodies there as American forces occupied the Japanese capital.
The way experts see it, these were no ordinary casualties of war, but possible victims of Tokyo's shadowy wartime experiments on prisoners of war -- an atrocity that has never been officially recognized by the Japanese government but is well-documented by historians and participants.
The neighborhood on the west side of Tokyo is deeply troubled.
"I feel sorry for remains with such a sad history," said Teppei Kuroda, a college senior who lives there. "I think they should be dug up and mourned properly."
Their first burial was anything but dignified.
Former nurse Toyo Ishii says that during the weeks after Japan's surrender on Aug. 15, 1945, she and colleagues at an army hospital at the site were ordered to bury corpses, bones and body parts -- she doesn't know how many -- before the Americans arrived.
A mass grave of between 62 and more than 100 possible war-experiment victims was uncovered in a nearby area in 1989. But Ishii's account -- publicly released in June -- could lead to a far larger number and a firmer connection to Unit 731, Japan's dreaded germ and biological warfare outfit.
"If the bones are actually there, they are likely related to Unit 731 itself, because the facility that used to stand in that part of the compound was closely linked to the unit," said Keiichi Tsuneishi, a Kanagawa University history professor and expert on Japan's biological warfare.
Ishii's disclosure led to a face-to-face meeting with Health Minister Jiro Kawasaki and a government pledge to investigate. But it may be a long time before anything is confirmed.
Health Ministry official Jiro Yashiki ruled out a speedy exhumation.
"People still live there, and we can't visit each family to remind them of the bones .... Just imagine how they feel about it," he said. "What if we find nothing after all the trouble?"
The 84-year-old nurse's story is the latest twist in the legacy of Japan's march through Asia in the 1930s and '40s.
From its base in Japan-controlled Harbin, China, Unit 731 and related units injected war prisoners with typhus, cholera and other diseases as research into germ warfare, say historians and former unit members. Unit 731 also is believed to have performed vivisections and frozen prisoners to death in endurance tests.
The 1989 discovery, during construction of a Health Ministry research institute at the former army medical school site in Tokyo, yielded dozens of fragmented thigh bones and skulls, some with holes drilled in them or sections cut out.
Police denied any evidence of a crime, and the bones weren't properly analyzed until two years later. In 2001 the ministry concluded that the remains -- many of them of non-Japanese Asians -- were most likely from bodies used in "medical education" or brought back from the war zone for analysis at the medical school.
The ministry said the bones could not be directly linked to Unit 731, though it acknowledged that some interviewees had suggested they were shipped from Manchuria, northern China, where the unit was based.
In 2002, the ministry built a memorial repository for the bones. But it has refused repeated requests for DNA tests from relatives of several Chinese believed to have perished at the hands of Unit 731.
Ishii says she was never involved in or knew about experiments on humans. Her account dwells on the final chapter of the war and the rush to conceal it.
In an interview at her Tokyo home, she said she was assigned to the hospital's oral surgery department in 1944.
She said the hospital had three morgues, where bodies with numbered tags around their necks floated in a formalin-filled pool, awaiting dissection. Body parts were preserved in bottles.
After the surrender, workers piled the bodies and bottles in carts and brought them to empty lots on the compound, she said.
"We took the samples out of the glass containers and dumped them into the hole," she wrote in a statement to the government in June. "We were going to be in trouble, I was told, if American soldiers asked us about the specimens."
She said a hospital official told her years later that a public housing complex for the families of senior doctors and hospital officials, including himself, was built at the site to cover up the mass grave. That complex was later replaced by Toyama No. 5.