Born in 1733 into the family of a domain physician in Obama Domain, Wakasa Province (Fukui). While studying Dutch medicine in Edo, he encountered the Dutch anatomical text "Ontleedkundige Tafelen" (Tafel Anatomia). On March 4, 1771, Genpaku, Maeno Ryotaku, and Nakagawa Junan attended a dissection at Kozukahara execution ground. They were astonished to find that what they saw inside the body matched the illustrations in the Dutch book — and on the spot, the three vowed to translate it. All but Maeno had essentially no Dutch. With no adequate dictionaries or grammars, they gathered daily and wrestled line by line; sometimes an entire day yielded only a single translated sentence. After more than three years of struggle, "Kaitai Shinsho" (A New Anatomy) was published in 1774. It became the foundation of modern anatomy and Western medicine in Japan, the starting point that took root the field of "rangaku" (Dutch learning). In his old age, Genpaku wrote "Rangaku Kotohajime," vividly recalling both the hardships and the exhilaration of those translation sessions. He lived to 83.

A man of action who believed in trying even the impossible. His reckless determination to translate from a language he barely knew changed the history of Japanese medicine. A curious and open-minded intellectual.

"Kaitai Shinsho" was the starting gun of modern Japanese medicine. By establishing rangaku, he paved the way for figures like Ogata Koan and Fukuzawa Yukichi, helping to lay intellectual groundwork for the Meiji Restoration.