横浜市立大学
Kosaka was born in Ise, Mie, and completed his M.D. in 1965 from Kanazawa University. He was appointed as a professor of psychiatry at Yokohama City University School of Medicine in 1991, before becoming a director of Yokohama City University Medical Center in 1995. He has been a director of Medical Care Court Clinic in Yokohama since 2011.