I recently got a copy of
'Między Warszawą A Tokio: Polsko-Japońska Współpraca Wywiadowcza 1904-1944' ('Between Warsaw and Tokyo: Polish-Japanese Intelligence Cooperation 1904-1944') by Kuroyama Hiraoki and Andrzej Pepłoński. As the title suggests, it discusses Polish-Japanese intelligence alliances during that period, such as attempts at secret support for each other against the common enemy in the Russo-Japanese war and the cooperation between Japanese and Polish agents during WW2 (which included getting documents for Jewish refugees to escape the Nazis and go to safety in Japanese territory). I think it's some fascinating history, just wish there was an English translation available to make the reading easier...