h. d. karunaratne received japanese government postgraduate research (monbukagakusho) scholarship to pursue his higher studies in yokohama national university, hitotsubashi university, nagoya city university and nagoya university from 1993 to 2000. subsequently, he joined japanese graduates' alumni association of sri lanka (jagaas) in 2000 and became an executive committee member in the same year. he was elected as the editor of the newsletter published by jagaas in 2004. he served as assistant secretary and vice president and secretary to jagaas, before being elected as the president of the association in 2014 and for the second time in 2018. he was an invited professor at the faculty of economics, hosei university, tokyo, japan from april 2006 to march 2008.