While still a student, he set a new unofficial world record for the triple jump, and was widely expected to secure the gold medal in the 1932 Los Angeles Olympics.

Ōshima also participated in the same event in the 1936 Summer Olympics in Berlin, but came in sixth place, while teammates Naoto Tajima and Masao Harada took the gold and silver medals, respectively.

Ōshima asked Hitler many questions on Nazi initiatives to improve on the physical education of German youth.

[2] After graduation from Kansai University, Ōshima was employed by the Mainichi Shimbun, working as a reporter in the sports section of the newspaper until retirement.

He then accepted the post of professor emeritus and later vice president of Osaka University of Health and Sport Sciences, where he undertook reforms of the athletic department to strengthen the Japanese team in preparation for the 1964 Tokyo Olympics.