Born in Gifu Prefecture, KUMAGAI went to Tokyo when he was a junior high school student, but he dropped out so to be a painter. In 1900, he entered the Tokyo School of Fine Arts, and studied under KURODA Seiki, FUJISHIMA Takeji and NAGAHARA Kotaro. There were AOKI Shigeru and KOJIMA Torajiro as classmates. He was mainly active in the Nika-ten. KUMAGAI started making Japanese-style paintings from 1938, and exhibited his drawings in India ink. He had worked alone without belonging to any societies since the Seiko-kai was dissolved in 1954. He also declined the Order of Culture in 1967. He had spent free days for painting. He died in Tokyo.