Matsunaga was born in Yaizu on September 21, 1914. In 1936, when he was a Tokyo Liberal Arts and Science University student, he was selected the Japan national team for 1936 Summer Olympics in Berlin. At this competition, on August 4, he debuted and scored a goal against Sweden. Japan completed a come-from-behind victory against Sweden. The first victory in Olympics for the Japan and the historic victory over one of the powerhouses became later known as "Miracle of Berlin" () in Japan. In 2016, this team was selected Japan Football Hall of Fame. On August 7, he also played against Italy. He played 2 games and scored 1 goal for Japan in 1936.