Eugenics has influenced political, public health and social movements in Japan since the late 19th and early 20th century. Originally brought to Japan through the United States (like Charles Davenport and John Coulter), through Mendelian inheritance by way of German influences, and French Lamarckian eugenic written studies of the late 19th and early 20th centuries. Eugenics as a science was hotly debated at the beginning of the 20th, in Jinsei-Der Mensch, the first eugenics journal in the Empire. As the Japanese sought to close ranks with the West, this practice was adopted wholesale, along with colonialism and its justifications.

The concept of pureblood as a criterion for the uniqueness of the Yamato people began circulating around 1880 in Japan, while eugenics in the sense of instrumental and selective procreation, clustered around two positions concerning blood, the pure blood (純血, junketsu) and the mixed blood (混血, konketsu).

Popularity of the pure-blood eugenics theory came from a homegrown racial purity or monoculture national belief that has been part of Japanese society since ancient times.^{[citation needed]} The local movement was however less focused on modern scientific ideals and more on the "outside person" vs the "native or inside person" and blood purity.

Later legal measures were supported by certain politicians and movements that sought to increase the number of healthy pure Japanese, while simultaneously decreasing the number of people suffering mental retardation, disability, genetic disease and other conditions that led to them being viewed as "inferior" contributions to the Japanese gene pool.

Opposition to the eugenics movement persisted amongst several right-wing factions, including members of the Diet of Japan and obstetricians, who perceived eugenics as suggesting that the Japanese people were only animals, not inhabitants of the "country of the kami" (神国, shinkoku) as believed by the Japanese national Shinto tradition. Yoshiichi Sōwa (曽和義弌), author of "Japan's Shinto Revolution", wrote in 1940, "When we look up into the past, the people of our country are descended from the kami. Are they claiming we must sterilize these people?"

Yamanouchi Shige (1876–1973), a plant cytologist, was one of the early and important members of the Japanese eugenics movement, who was trained under John Merle Coulter (1851–1928) an American eugenicist and botanist. He was a major promoter and academic of early Lamarckian theory, but later blended his ideas with Mendelian evolutionary theory.

His career is a direct link between United States and Japanese eugenics. His approach has been credited with searching for a way for the Japanese race to genetically surpass what was then the "dominant Western race" of the 19th and early 20th centuries by breeding smarter and stronger Japanese people.

According to Jennifer Robertson of the University of Michigan, eugenism, as part of the new scientific order, was introduced in Japan "under the aegis of nationalism and empire building." She identifies "positive eugenism" and "negative eugenism." Positive eugenism, promoted by Ikeda Shigenori, refers to "the improvement of circumstances of sexual reproduction and thus incorporates advances in sanitation, nutrition and physical education into strategies to shape the reproductive choices and decisions of individual and families" Negative Eugenism, promoted by Hisomu Nagai, "involves the prevention of sexual reproduction, through induced abortion or sterilization among people deemed unfit". "Unfit" included people such as alcoholics, lepers, the mentally ill, the physically disabled, and criminals.