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 US 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 live prisoners of war -- an atrocity that has never been officially recognized by the Japanese government.
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.
Former nurse Toyo Ishii says that during the weeks following 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 yield 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 wartime 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 rules 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 [would] 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 rampage through Asia in the 1930s and 1940s.
According to historians and former unit members, from its base in Japan-controlled Harbin, China, Unit 731 and related units injected war prisoners with typhus, cholera and other diseases as part of their research program into germ warfare. Unit 731 is also believed to have performed vivisections and frozen prisoners to death in endurance tests.
The 1989 find, during construction of a Health Ministry research institute at the former army medical school site in Tokyo, revealed 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 were not 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, 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 in Unit 731.