Yagi was born in Muroran, Hokkaidō, and graduated from Waseda University in 1938 with a degree in French literature.

As a writer, he was a devotee of Fyodor Dostoyevsky and Takeo Arishima, and received the 1944 Akutagawa Prize for 劉廣福 Ryūkanbu[1] and the 1976 Yomiuri Prize for Kazamatsuri.

[2] Some of his materials are now exhibited in Muroran's Literature Museum.

His Dharma name was Keiunin Zuishin Gitoku Koji (景雲院随心義徳居士).

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