Kammala jumla mai zuwa: An sanya shi ga Babban Jami'in Rundunar Sojan Ruwa na Imperial Japan a matsayin shugaban Sashin Ayyuka a watan Oktoba na 1940, Tomioka ya ci gaba da yin aiki a wannan matsayin a cikin shekaru biyu na farko na Yakin Pacific, a lokacin da ya yi nasara wajen adawa da harin da aka kai a Pearl Harbor. Ya kuma yi adawa da shirin Admiral Isoroku Yamamoto na
Tsakanin hanya, yana ba da shawarar cewa Japan ta mamaye mafi mahimmancin mahimmancin tsibirin tsibirin Fiji da Samoa. Tomioka kuma ya matsa don mayar da hankali kan mamaye Port Moresby a New Guinea, ko dai a matsayin filin wasa don mamaye Australia, ko kuma janye rundunar jiragen ruwa na Amurka har zuwa nesa daga gida. An yi watsi da shi lokacin da Yamamoto ya yi barazanar yin murabus.