[2] Itô was a member of the faculty at University of Kyoto for most of his career and eventually became the director of their Research Institute for Mathematical Sciences.

[4] Itô was born on 7 September 1915 in a farming area located west of Nagoya, Japan,[4] that being the town of Hokusei-cho in Mie Prefecture.

[7] In 1943, he was appointed an assistant professor at Nagoya Imperial University,[5] where he benefited from discussions with the mathematicians Kōsaku Yosida and Shizuo Kakutani.

[8] From investigations done during this period he published a series of articles in which he defined the stochastic integral and laid the foundations of the Itō calculus.

[6] These works were published despite the difficulties of life in Japan during World War II, including problems accessing libraries and especially the loss of contact with Western mathematicians and the lack of awareness of results from them.

[3][5] For instance, the only other Japanese mathematician actively interested in Itô's work during the war, Gisiro Maruyama, read a mimeographed copy of a paper while in a military camp.

[4] He was at the Institute for Advanced Study from 1954 to 1956 while on a Fulbright fellowship;[6] while there he worked closely with William Feller and Henry McKean who were at nearby Princeton University.

[4] When Itô left Cornell and returned to the University of Kyoto, he served as director of their Research Institute for Mathematical Sciences.

[2] He also had a post-retirement position as a professor at the private Gakushuin University for several years,[6] a common practice among higher-ranking Japanese academics.

[2] As he due to his health was unable to travel to Madrid, his youngest daughter, Junko Ito, received the Gauss Prize from King Juan Carlos I on his behalf.

[10] Later, IMU President Sir John Macleod Ball personally presented the medal to Itô at a special ceremony held in Kyoto.