Sadamasa Motonaga was born in 1922 in Ueno city, Japan. He graduated from Mie Prefecture Ueno Commercial School in 1938 aspiring to become a manga artist. He started painting figural and landscape works on canvas under the tutelage of Mankichi Hamabe. When in 1952 he moved to Kobe, he experimented the abstract painting and he made sculptures using a combination of natural and industrial materials (such as wood, water and plastic). In 1953, his work Kiiro no rafu (Yellow Nude) won the Holbein Prize at the Ashiya City Art Exhibition, capturing the attention of Jiro Yoshihara. Two years later, in 1955, Yoshihara invited Motonaga to join the Gutai Art Association, a group of radical post-war artists in Japan, and to participate to the group’s exhibition “Modern Art Outdoor Experimental Exhibition to Challenge the Midsummer Sun” in Ashiya Park. In this occasion, Motonaga created his most famous site-specific installation Work (Water) made by vinyl tubes filled with coloured water and hanged to the trees’ branches. He was then invited by the Japan Society to spend one year in New York from 1966 to 1967, followed by some time in Europe. Thanks to this period spent abroad, inspired by the traditional tarashikomi technique in which layers of paint are allowed to pool irregularly, he developed a technique using acrylic paint and airbrush. This new technique led in 1970 to a more peculiar style of intense, vivid and coloured saturated paintings and humorous titles. Back to Japan, he left the Gutai group in 1971 and began making silkscreen prints, tapestry, chair design and illustrations for children’s books. Throughout his entire life he received prizes for Excellence at the Contemporary Art Exhibition of Japan and other several awards and culture merit. In 2011, the Guggenheim in New York commissioned him to recreate the Work (Water) for the 2013 exhibition “Gutai: Splendid Playground”. He died in Kobe in 2011.