Sugataro Yabuki (known as Sen Katayama), founding member of both the American and Japanese Communist parties, was born to Kunizo and Kichi Yabuki in 1859 in the Hadeki district of what would become Okayama prefecture after Japan's Meiji Restoration in 1868. The second son of peasant parents, Sen was adopted into the Katayama family at age nineteen, thereby becoming a "first son." His mother, Kichi, who had been deserted by her husband and estranged from his family, had encouraged her son to become a teacher, and the adoption was in part to facilitate that goal by enabling him to avoid conscription, further his education, and ultimately get to Tokyo, the capital of the new "modernizing" Japan. In Tokyo, while working as an apprentice printer, he studied at a small preparatory school, the Oka Juku, where he formed a lifelong friendship with a rich boy, Iwasaki Seikichi, whose uncle was one of the founders of the Mitsubishi company. Iwasaki, who had a plan to go to America, was beginning to learn English, and he inspired Sen to do the same. After young Iwasaki went off to Yale, Sen managed to work his way to America and ultimately into Grinnell College, from which he graduated in 1892. From 1892 to 1894 he attended Andover Theological Seminary, and he spent the following year at Yale Divinity School. In the process of liberal and theological studies and many hard knocks, Sen became a Christian and a socialist. He returned to Japan in 1896, became the director of a settlement house called Kingsley Hall, and was soon immersed in social causes, which came to include labor organizing and antiwar activities in opposition to the Japanese government. His good friend from student days, Iwasaki, perhaps to get him away from radical activities, urged him in 1903 to return to America to look into rice-planting opportunities. Sen had kept up his interest in America, teaching English and publishing a "Student's Guide to America." Needing a "good rest" from seven years of "toil" in social causes, he accepted Iwasaki's offer of financial assistance for the trip. On his trip he attended the Second International Socialist Congress in Amsterdam, Holland, and an American Socialist Party convention in 1904 in Chicago. However, his main business had become rice growing in Texas, where he lived and worked most of the time from February 1904 to January 1907.
In Houston he became friends with a Japanese restaurant owner, Tsunekichi Okasaki, in whose restaurant he worked for a time as a waiter and cook. There were already Japanese farmers at Garwood, but they disapproved of his attending socialist conventions, so after the conventions he decided to settle down at Aldine, where he purchased a 160-acre farm in October 1904. He worked hard, but his rice crop failed, and he had to return to work in Okasaki's restaurant after the hot summer of 1905. But he felt that the failure had been because the project had been too small, and at the restaurant Sen and Okasaki decided to try a large venture, forming a partnership to do so. Okasaki purchased 10,202 acres of land in Live Oak and McMullen counties, and in December 1905 he and Sen returned to Japan to get money from Iwasaki and obtain laborers for the rice fields. Iwasaki backed the project enthusiastically, with $100,000 and the formation of a Nippon Kono Kabushiki Kaisha (Japan Farming Company) to develop the Texas project, and he appointed Sen Katayama managing director on condition that he "promise to stop working publicly as a socialist." Sen seems to have agreed, with the thought that he would leave the socialist cause in other hands for the time being, and he returned to Texas. Okasaki, as number two in the company management, remained in Japan to recruit workers, where he had some difficulty due to Katayama's radical reputation. When Okasaki returned to Texas he found that Katayama had "violated his pledge" by bringing some of his American socialist friends into the directorship of the company. (Texas law required that the majority of the company stockholders be American citizens). The result was a bitter quarrel. Okasaki complained to Iwasaki, and Iwasaki recalled Sen Katayama to Japan and dissolved the company. After leaving Texas Sen Katayama returned to Japan in 1906 where he remained active in the Socialist movement and pursued a career in journalism. His participation in the Tokyo Streetcar Strike of 1912 resulted in his imprisonment, and after his release he left Japan for good. He returned to the United States and resided mostly in California. Disillusioned with socialism and attracted by the success of the Bolshevik revolution of 1917–18, Sen became a communist. In his capacity as an officer for the Comintern he was sent to Mexico in 1921 and later that year was called to Moscow, where he was hailed as one of the leaders of the Japanese Communist movement. Sen remained in the Soviet Union until his death on November 5, 1933. He was buried in the Kremlin. Sen had two children by his first wife, Fude, who died in 1903, and another daughter by his second wife, Hari Tama, whom he married in 1907.