米澤藩
Kobayashi was a native of Yonezawa, Yamagata, where his father was a farmer. With the assistance of a clique of admirals within the Imperial Japanese Navy from former Yonezawa Domain (including Yamashita Gentarō and Chūichi Nagumo), he entered military preparatory schools and graduated 4th out of 149 cadets from the 38th class of the Imperial Japanese Navy Academy. His classmates included Michitaro Totsuka, Takeo Kurita, Rokuzō Sugiyama, Gunichi Mikawa and Aritomo Gotō.