Like many young engineers at the time, Hosaka left university and went straight into industry, joining the Honda Motor Company in 1972. He worked his way through the ranks to become the general manager of the automotive planning division in 1993. After two years in that job he was appointed the head of Honda Resaerch & Development in the Americas. In 1997 he was recalled to Japan and put in charge of Honda Research & Development, the elite division of the Japanese car company with responsibility for the company's racing activities. He was later replaced in that role.