Studied briefly at the Fifth Higher School in Kumamoto and then at the Waseda Semmon Gakko (predecessor of Waseda University).
Teisuke Oki led a Bohemian life and went to China (1901), became a teacher at the Tobun Gakusha School in Peking and founded the Bummei Gakusha School (1903). When the Russo-Japanese War broke out in 1904, he and Shozo Yokogawa became secret agents of the Japanese Army. Upon their plan of blasting a railway bridge spanning the Amur River becoming known to the Russians, they were captured and sent- to Harbin, where a Russian court-martial sentenced them to death. A stone memorial was erected at the spot in Harbin where they were shot by a firing squad.