Most of those Japanese POWs who survived the winter of 1945 / 46 had been repatriated by 1956, with mediation by the Red Cross.
Furthermore:
In 2005, the Russian government provided the Japanese Ministry of Health and Welfare microfilms of personal information of 40,940 Japanese POWs who had died during their detention.
Still horrific but less than 10% of the total number.
There is a fascinating history of those who returned to Japan but couldn't fit-in again due to Soviet indoctrination.