Born in Ibaraki Prefecture in 1931, Ay-O, together with On Kawara and others, joined the Demokrato Artists Association—an artists’ association formed around EiQ, an avant-garde artist who represents postwar Japan—in 1953. He attracted attention with works he presented in such exhibitions as the Demokrato Exhibition and the Yomiuri Independent Exhibition. He also became acquainted with the art critic Sadajiro Kubo around this time, which led him to become more active in printmaking. At the time, prints were still considered to be a lower art form than such mediums as oil painting and sculpture. Ay-O contributed to moving prints onto the center stage of artistic expression, along with other Demokrato members such as Masuo Ikeda, and the medium eventually came to hold an important position in his work. In 1958, Ay-O traveled and relocated to New York. There, he joined the avant-garde art movement ‘Fluxus’, led by George Maciunas, and took on the challenge of working with a variety of different forms of expression. As a Fluxus member, he participated in performances, known as 'events,' by creators from different fields such as artists and musicians, and created works with the new concept of ‘multiples’ which made them available to a greater number of people. He also made installations known as ‘environments,' which could be touched and experienced by the viewers. Finally, he rebelled against the concept of creating works consisting of lines, instead filling his motifs with the colors of the rainbow, from red to violet. Ay-O’s experimentation with this style was expressed in a variety of genres including prints, paintings, and installations, bringing him international renown as ‘The Rainbow Artist’.