[1] Tokutomi was born on December 8, 1868, in Minamata, Japan, to a samurai family.

He converted to Christianity in 1885, and moved to Imabari, Ehime, where he lived with Shiro Sokabe and was a student of Tokio Yokoi.

Their correspondence is on display in the small museum located in the Roka Kōshun-en Park, along with belongings.

From February 27, 1907, until his death, he lived in a house in Musashino (Setagaya, Tokyo, Japan).

Tokutomi died on September 18, 1927, in Ikaho, Gunma, one day after reconciling with Sohō.