Shi ne dan asalin Kōchi Prefecture, kuma ya kammala karatun aji na 20 na Kwalejin Sojojin Jafananci a 1908. 'Yan ajin sa sun hada da Yarima Asaka, Yarima Higashikuni Naruhiko, Yarima Kitashirakawa Naruhisa, Mitsuru Ushijima, Heitarō Kimura, Takashi Sakai, da Shōjirō Iida. Daga baya ya kammala karatu daga aji na 28 na Kwalejin Ma'aikatan Sojoji a 1916. Bayan ya yi aiki a cikin ma'aikata da matsayi na gudanarwa a cikin Janar Janar na Sojojin Japan, an tura Shimomura zuwa Faransa a matsayin mai ba da shawara na soja a shekarar 1919. Ya koma Ofishin Dabaru da Shirye-shiryen Janar Janar a 1921. Ya shiga cikin tawagar Jafananci zuwa tattaunawar Geneva na Naval daga 1928-1919 da kuma a 1931. Daga 1935 zuwa 1939 ya kasance kwamandan Janar na 1st Army Regiment, Yarima Kitashirakawa Naruhisa, Mitsuru Ushijima, Heitarō Kimura, Takashi Sakai, da Shōjirō Iida. Daga baya ya kammala karatu daga aji na
Ofishin Dabaru da Shirye-shiryen Babban Jami'in