This work is titled Proof of Peace AU 33. In 1976, Shimamoto was nominated as the leader of AU, a group of new artists, to help members across Japan create and publish their art. AU, originally an acronym for Artist Union, was established in 1975 by the founder of Japanese Neo-Dadaism, Masunobu Yoshimura. In 1980, AU changed its name to stand for Art Unidentified, and became active in the international art world. The piece of brown kraft paper at the center is a main feature in this joint project. By adding the element of collage to the bottle-throwing foundation, the work becomes more layered and three-dimensional visually. Shimamoto shattered bottles of paint against the canvas, rendering the dynamic colors in this painting deconstructed by disorder, with the glass smithereens scattered on it. The blue collides with the bright yellow, producing an emerald color, and realigning all the coincidences. Slowly, Shimamoto transferred action into two-dimensional works. At the same time, famous artists in the West, such as Lucio Fontana and Hans Hartung, were also emerging onto the world art stage with "action painting".

Shimamoto was the publisher of the Gutai journal. His Heiwa No Akashi X AU (Proof of Peace) series served as the best ambassador for Gutai, connecting Japanese and international art circles. This led to Gutai's exchange with the giant of American post-war abstract expressionism, Jackson Pollock, and the father of American mail art, Ray Johnson. Shimamoto also published treatises on how painting tools and paintbrushes constrain art, as well as his theories on beauty. In recent years, the art world has reaffirmed the importance of Gutai as a post-war art movement. With a high demand from collectors in the west coast of the US, a work of Gutai art has since become a common component in all great art collections. Shimamoto’s works are housed in the Tate Museum in London, the Centre Pompidou in France, and the Galleria Nazionale d'Arte Moderna e Contemporanea in Italy.