Michel Tapié, in his 1957 text “A Mental Reckoning of my First Trip to Japan” originally published in Bijutsu Techo, singled out Shimamoto from the Gutai group along with Yoshihara, Kazuo Shiraga and Atusko Tanaka as “four artists who should appear alongside the most established international figures.” Shimamoto expressed his belief that Gutai would have been more original and experimental had Taipé not influenced the group’s direction so heavily. He remained a member of Gutai until 1971, a year before the group officially disbanded with the death of Yoshihara. Shimamoto’s departure stemmed from disagreements over finances within the group over Gutai’s participation in Expo ‘70, the first World’s Fair in Asia and a landmark event for Japanese contemporary art.