Yasuo Sumi starts painting while working as high school teacher alongside with Shozo Shimamoto, one of the founding members of Gutai Art Association. Sumi who uses soroban (Japanese abacus) as the material of teaching mathematics, discovers by chance that there is beautiful trace left after rolling painted soroban on paper. Since then, soroban becomes synonym for Sumi’s technique as well as vibrator and traditional umbrella. Sumi joins to Gutai in 1955 and continues to exhibit his works at each subsequent Gutai exhibition until its disbandment. The number of improvisational creations reflected his three principals “desperation, absence of seriousness, irresponsibility” is praised by the leader of Gutai, Jiro Yoshihara. As well as Shimamoto, Sumi experiences many exhibitions in Europe and USA, gets popularity especially in Italy.