Tōson was educated in Tokyo at Meiji Gakuin, where he was also baptized, although Christianity did not lastingly affect either his life or his thought. In the early 1890s he began to write poetry and joined the short-lived romantic movement of young poets and writers, which he later described in his novel Haru (1908; “Spring”). The first of his major novels, Hakai (1906; The Broken Commandment), the story of a young outcast schoolteacher's struggle for self-realization, has been called representative of the naturalist school, then the vogue in Japan, although it more clearly reflects the influence of Jean-Jacques Rousseau than of Émile Zola. Ie (1910–11; The Family) depicts the stresses Japan's modernization brought to his own family. Shinsei (1918–19; “New Life”) narrates the unsavoury affair of a writer with his niece in a manner that carries the confessional principle to embarrassing excesses.

Tōson began research in 1928 for Yoake mae (1935; “Before the Dawn”), his greatest work and one of the masterpieces of modern Japanese literature. This is a story of the struggle for the Imperial Restoration in the 1860s as mirrored in a rural community. The tragic hero of the novel, modeled after the writer's own father, eventually dies an embittered death, convinced that the cause of pure patriotism had been betrayed by the glib modernizers of post-Restoration Japan. A final novel, Tōhō no Mon (“Gate to the East”), incomplete at his death, seems to invoke the Buddhist wisdom of medieval Japan as a way out of the impasse of the present.