Facts are disputed. The wikipedia articles cover these topics pretty well:
https://en.wikipedia.org/wiki/Allegations_of_biological_warfare_in_the_Korean_War
Discussion
I'm reading. What comes to mind:
-nazi Germany was also doing human experiments. As Japan was their partner I believe they could do the same
-it always impresses me that Japan came out as the victim from WW2 (due to atomic bombs). My Korean friends says more Korean and Chinese slaves working in Japan died when the bomb dropped than japanese.
This whole stuff of painting Japan ad victim is highly suspicious
Oh yes, they were ruthless dominators, and they started the biological weapons stuff.