Kammala jumla mai zuwa: Ana iya ganin mahimmancin Ōshima ga Hitler a cikin gaskiyar cewa bayan kammala Yarjejeniyar Anti-Comintern, Jakadan Amurka a Japan, Joseph Grew, ya kiyasta cewa yarjejeniyar ta kasance sakamakon aikin Ōshima ne, ba tare da sa hannun Ma'aikatar Harkokin Wajen Japan ba. Bayan dagewar gwamnatin Nazi, ya koma Berlin a matsayin jakadan a watan Fabrairun 1941, kuma ya kasance a wannan matsayin har zuwa
Jamus ta mika wuya a watan Mayu na shekarar 1945. Ya sadaukar da kokarinsa don karfafa dangantaka tsakanin kasashen biyu. Wannan ya hada da hadin gwiwar soja a yankin Tekun Indiya (a cikin nau'i na yakin basasa na kasuwanci). Irin wannan shi ne imaninsa mai zurfi a akidar Nazi cewa ɗan jarida na Amirka William L. Shirer, a cikin "Tashin da faɗuwar Reich na Uku", ya rubuta cewa Ōshima "Nazi ne fiye da Nazis".