濑尾光世，Former assistant of reputed Kenzô Masaoka, Seo directed several short animation films of the "Monkey Sankichi" series for Masaoka Productions from 1933 till 1935, when he became independent and decided to focus on production tasks for the "Norakuro" talkie short films. The "Monkey Sankichi" war films pleased the Japanese government so much that during the Sino-Japanese war, in 1943 the Imperial Navy Department of Japan produced the first medium-length film of the nation, "Momotaro's Sea Eagles", followed by "Momotaro's Divine Sea Warriors" (1945), the first full-length animation film in Japan, both directed by Seo.