https://en.wikipedia.org/wiki/Unit_731
https://ahf.nuclearmuseum.org/ahf/history/unit-731/
And a web site created to document this. https://unit731.org/
Unit 731 was a very small thing in comparison to Japanese atrocities in the Philippines. And THAT was small thing in comparison to what the Japs did to the Chinese.
The sheer mass of cruelty is overwhelming. It’s endless, repetitive with no finality. If you do a deep dive it can get extremely depressing. It’s why, probably, Iris Chang committed suicide after researching her book on Nanking.
Paul Scott (”Rampage”, 2018, on the Manila massacre Feb-March 1945), commented on this. The number of cases is numbing.