Rich Ting portrays the IJA Captain in The Man in the High Castle. How did Chief Inspector Kido suspect that he killed Trade Minister Tagomi?
I'm assuming that before he secretly recorded their conversation, Kido must've suspected him.
I don't have the script to hand, but General Yamori recommends Captain Iijima as "a man we can trust" when ordering the surveillance of the Admiral.
This tips Kido off that the General has probably had Iijima carry out some similarly questionable actions in the recent past.