Hisao Domoto was a front-line painter of contemporary art who led the post-war Japanese art scene. Born in Kyoto and having Insho Domoto, a great master of modern Japanese art as his uncle, Hisao graduated from Kyoto City Technical School of Art. While he was selected for Nitten in 1948, Hisao, who was unsatisfied with Japanese painting circles, moved to Paris in 1955. He participated in the Informel movement flourishing at that time. His works did not stay in a single style but changed from one to another and were highly acclaimed in international exhibitions such as the Venice Biennale and the Sao Paulo Art Biennale. Critical state refers to a state where the production rate and the loss rate of neutrons in a chain reaction are balanced. In the Critical State series, the S-shaped pattern covering the surface of paintings of the Chain Reaction series is overlaid with concentric squares as if to repeat the rectangular shape of the canvas. Drips from the paint for concentric squares drawn over the horizontal structure of rhythmical perfect circles add verticality and achieve the two-dimensional structure established in Domoto’s paintings in a more complex style. The series is an excellent example representing a culmination of Domoto’s paintings.