Kiyoshi Nagai was born in Tokyo and graduated from the Nihon University in 1932. He studied western painting techniques at the Tokyo School of Fine Arts. He is more widely known under the name Hiroyuki Tajima.
Nagai began creating woodblock prints in 1946 and he signed his richly colored abstractions, Tajima, and his more literal works, Nagai. He was a member of the Bijutsu Bunka Kyokai (a group of abstract and surrealist artists) and in 1963 he joined the Japanese Print Association.
Nagai took part in the International Tokyo Print Biennale and his works are represented in numerous collections worldwide.