Yoshio Kôsaku was a Rangaku expert and one of the chief official Dutch translators stationed in Nagasaki. This position was passed down within the Yoshio family, and their house, which came to contain a great many Dutch/Western artifacts over the years, was sometimes known as Kômô yashiki ("the Dutch mansion," or "Mansion of Red-Hairs"). Kôsaku is also known for writing a preface for the Kaitai shinsho.
Kôsaku inherited the position of official Dutch translator in 1748. He studied Dutch medicine under the opperhoofd (head) of the Dutch East India Company base in Nagasaki, and started his own "Kôsaku school/style" of medicine. His students included Maeno Ryôtaku and Sugita Genpaku, and he met with numerous Rangakusha who traveled to meet him and learn more firsthand about the Dutch, including Furukawa Koshôken and Shiba Kôkan.
- Yonemoto, Marcia. Mapping Early Modern Japan. University of California Press, 2003. pp86-87.
- "Yoshio Kôgyû." Digital-ban Nihon jinmei daijiten デジタル版 日本人名大辞典. Kodansha 2009.