After graduation, Shunsō was commissioned by the Imperial Household Museum (now the Tokyo National Museum) to copy important religious paintings at Buddhist temples in Kyoto and Nara, and he also became a teacher at the Tōkyō Bijutsu Gakkō (present-day Tokyo University of the Arts)). In 1898, he joined Okakura Tenshin in establishing the Nihon Bijutsuin. From 1903 to 1905, he traveled extensively overseas, holding exhibitions of his works in India, the United States and in Europe.
After his return to Japan, Shunsō successfully competed in many national exhibitions in Japan, including the government-sponsored Bunten.
Shunsō developed a new painting method, derogatorily named by his contemporaries as moro-tai (vague style). This new method used a gradation of colors to replace the line drawings that characterized traditional Japanese-style painting. This new style, however, gained little support from Shunsō's contemporaries and was severely criticized by art critics. Shunsō came to realize that while moro-tai was effective in depicting such scenes as morning mist and evening glow, its color gradation technique proved good only for those limited motifs. Shunsō began integrating his original moro-tai with line drawing to overcome this disadvantage, and his later works exhibit a new style which came to typify the Nihonga genre, distinguishing it from the more restrictive styles of traditional Japanese-style painting.
In his final years, Shunsō suffered from renal, or kidney disease. Driven by fear of blindness, Shunsō painted frantically whenever his illness entered a state of remission. In 1909, his work Ochiba won the highest award at the third Bunten Exhibition. It is now designated an Important Cultural Property by the Japanese government's Agency for Cultural Affairs and is now in the collection of the Eisei Bunko Museum, Tokyo. His representative work "Ochiba" is based on the motif of a thicket of trees around Yoyogi, Tokyo, Japan, which was still a suburb at the time. His work Black Cat (1910) has also been designated an Important Cultural Property. In 1911, he died of kidney disease (nephritis) just before his 37th birthday.