The remains of eight soldiers who died in the 1939 Battle of the River Halka, known as the Nomonhan Incident, were repatriated and placed in a mortuary in the health ministry Thursday.
They will be handed over to relatives if they are identified through DNA and other forensic tests.
The remains were collected near the border of Mongolia and China between July 31 and Aug. 5 by officials of the Health, Labor and Welfare Ministry, and relatives of soldiers who died in the battle 66 years ago.
"There are still many more remains remaining, and we wish to bring as many of them back to Japan as possible," said Masaharu Abe, 68, a relative of a soldier.
In January last year, Mongolia gave Japan permission for the first time to collect and bring home remains. A government team brought back 16 sets of remains in total, but not all have been identified.
Some 8,000 Japanese soldiers died in the battle, which took place with Soviet and Mongolian forces from May to September 1939 near the border between Mongolia and what was then Japanese-occupied Manchuria in northern China. About 4,500 bodies were taken back at the time, but 3,500 are believed to have been left in the region.