Momaru was a Western-style painter who studied with Okada Saburosuke (1869-1939). Immediately after graduating from the Tokyo School of Fine Arts in 1909, he took up teaching duties in colonial Korea. He served at the Kyongsong (Gyeongseong) Middle School (a school for Japanese students that later became the Seoul Middle and High School) and stayed in Korea until 1945. In the early 1950s he began designing woodblock prints for the publisher Kyoto Hangain. Most of these works consist of scenes of Korean customs and scenic places. Typically, they are signed M. Hiyoshi with a stylized seal for the name Mamoru.