 After returning to Japan in 1960, Kaga took up university teaching, and was a psychology professor at the Tokyo Medical and Dental University (1965-1969) and Sophia University (1969 - 1979).Kaga wrote several novels based on his time in France, including "Arechi o tabi suru monotachi" (Travelers through the Wasteland) and "Furandoru no fuyu" (Winter in Flanders) which won the Minister of Education Award for New Artists in 1968.His 1973 novel "Kaerazaru natsu" (帰らざる夏, A Summer Long Gone), on the tragic consequences of a young man's military indoctrination during World War II received the Tanizaki Prize.