Genpaku started learning his family business, medical science, in his adolescence; he studied western medicine under Gentetsu NISHI, a feudal doctor, and Chinese medicine under Ryumon MIYASE, a Confucian belonging to School of Ancient Learning and a founder of the medical school in Hongo (Bunkyo Ward, Tokyo).
青年期には家業の医学修行を始め、医学は奥医の西玄哲に、漢学は本郷(文京区)に開塾していた古学派の儒者宮瀬竜門に学ぶ。