According to Matsuno, Japan’s WWII-related records have been transferred to the National Archives of Japan (NAJ) by the Ministry of Health, Labour, and Welfare, while some diplomatic and military-related documents are kept by the Ministry of Foreign Affairs and the Ministry of Defense.
Every once in a while, the NAJ would release batches of newly processed historical materials, among which Matsuno spotted the recently discovered documents.
The researcher pointed out that even when new materials are made available, they can remain obscure without substantial expertise and research skills, as searching for information using keywords like “Unit 731” or “epidemic prevention unit” yields little results.