Say was born on Aug. 28, 1937, in Yokohama, Japan. As a youth he loved to draw, but his father, a businessman, wanted him to pursue other interests. Nevertheless, at age 12 Say apprenticed himself to cartoonist Noro Shinpei, who taught him Western and Japanese drawing styles. The relationship with his mentor later inspired Say's young-adult book ‘The Ink-Keeper's Apprentice' (1979).

Say came to the United States at age 16 and attended various art institutes in California. His architectural studies at the University of California at Berkeley ended when he was drafted into the military. He was sent to Germany and trained as a firing-panel operator of a missile system. Upon his return to the United States Say became a writer, illustrator, and commercial photographer.

Among the publications Say both wrote and illustrated were ‘The Bicycle Man' (1982), ‘A River Dream' (1988), ‘El Chino' (1990), ‘Tree of Cranes' (1991), ‘Stranger in the Mirror' (1995), and ‘Emma's Rug' (1996). His illustrations, often in pen and ink or watercolors, also appeared in works by other authors. He was a runner-up for the 1989 Caldecott Medal for his pictures in Dianne Snyder's ‘The Boy of the Three-Year Nap' (1988); the Japanese folktale about a lazy boy outwitted by his mother also received the Boston Globe–Horn Book Award in the picture-book category. ‘How My Parents Learned to Eat' (1984), with text by Ina R. Friedman, received the 1985 Christopher Award.