I came across this guy somehow: https://en.wikipedia.org/wiki/Kenji_Doihara
I’m not an easy reader, but I read the Wikipedia page cover to cover in one go. It’s something.
He reminded me of the highly entertaining profile Indy did on Basil Zakharoff. Doihara comes across as, to be honest, evil himself. But if you want to make profiles on the personalities of WW2, this one will be a pretty wild ride. Lesser known to be sure, but also fascinating.