Born in 1801 to a farming family in the domain of Saga in Hizen. Setting himself on medicine while young, he studied under Koga Kokudō in Saga and then entered Siebold's Narutaki-juku in Nagasaki, mastering Rangaku and Western medicine. He opened a practice in Edo and worked to spread Western medicine as a physician of the Saga domain. In 1858, with shogunal permission, he established with his own funds the Otamagaike Vaccination Center at Kanda Otamagaike in Edo, spreading Jenner's vaccination. The same year he was appointed an okuishi (chief shogunal physician), becoming the first scholar of Western medicine to reach the highest rank of shogunal doctor. In 1859 the Otamagaike Center was taken over by the shogunate, later becoming the Institute of Western Medicine and its medical school, and ultimately the origin of the University of Tokyo Faculty of Medicine. He died in 1871 at 71, having lived to see the Meiji Restoration.

Gentle yet tenacious, with keen political sense. Amid fierce resistance from Chinese-medicine doctors against Rangaku practitioners, he avoided direct confrontation while persistently persuading the shogunate and establishing the standing of Western medicine. A scholar who also demonstrated outstanding ability as an organizer of medical administration.

The Otamagaike Vaccination Center Genboku opened was the start of public institutional Western medical education in Japan and forms the origin of the University of Tokyo Faculty of Medicine. Through his efforts, vaccination against smallpox spread across the country, making a major contribution to population maintenance in the late Edo and Meiji eras. His former residence in Kanzaki, Saga Prefecture, still stands and is a city historic site. His achievement in placing Western medicine at the center of the shogunate endures as the starting point of modern Japanese medicine.