In 1951 goes to Tokyo to start a career as a cartoonist, but begins to work in the Anti-drug Department Office of Kanto Koshinetsu. During these times he was very impressed by french and soviet animation films and finally enters in 1956 in an animation studio which later will be Toei Doga, the most important animation studio in Japan. He enters in a group of pioneers under the orders of legendary Akira Daikuhara, and soon will be speciallized in the animation of action secquences. After the short film "Dream Baby" (1958), the Daikuhara team collaborate in the first colour long feature films of this company, "The White Snake Enchantress" (1958) and "Young Sasuke Sarutobi" (1959). "Prince of the Sun: The Great Adventure of Horus" (1968) was the first official collaboration of the team Ôtsuka-Kotabe-Takahata-Miyazaki and Ôtsuka's debut as animation director. In 1969 he quits Toei Doga to enter in the little animation studio A Pro. [later called "Shin'Ei" (New A)] which worked as independent unit under the Tokyo Movie Studio. Ôtsuka is appointed chief animation director of the studio and worked in the failed pilot film of "Lupin III", the first animation movie of Monkey Punch's comic in 1971. Later he directed the animation of two of its sequels, "Lupin III: Castle of Cagliostro" (1979) and "Lupin III: The Conspiracy of Fuma Family" (1987), which was his last and most personal film. From this year he undertakes the guidance of young animators.