Iwase was born in 1904 in Onjuku, a coastal fishing village on Japan’s Boso peninsula in Chiba Prefecture. In 1924 he graduated from Tokyo’s Meiji University with a degree in law and went on to oversee his family’s sake distillery. Not long after he began documenting the vanishing traditions of Japan’s coastal life which became a lifelong passion for him. One subject he concentrated on was the bare breasted female divers known as ama, who due to their gender could brave cold water temperatures during the summer months diving for shellfish and seaweed. As Mr. Iwase’s passion for photography deepened, his technique evolved through his associations with other important photographers such as Kiichi Asano, Kira Sugiyama,Tadahiko Hayashi and Shotaro Akiyama. He became a pioneer of the Japanese modernist nude and also documented traditional culture in postwar Japan.

Beginning in 1933 Iwase held his first of many solo exhibitions, including six shows in Chiba Prefecture and two in Tokyo. The latter included the Matsuya Department Store Gallery in 1933 and the Takarazuka Theatre in 1950. In 1976 he participated in the 100th Year Photo Exhibition at the Seibu Gallery in Tokyo, sponsored by the Photographic Society of Japan. During his life Iwase received numerous awards and citations for his work. He passed away in 2001 at the age of 97. His work is also held in many collections including the Tokyo Metropolitan Museum of Photography. He published two Japanese volumes of his work with the first being the privately printed 1983 title; Ama no Gunzo Chiba Onjuku 1931-1964 (Group Images of Chiba’s Onjuku Ama Divers 1931-1964), and a second revised edition published by Maruzen in 2002 that included additional images of coastal life in Onjuku.