Rikio Kozu joined the Nippon Steel Corporation in 1979 and began his trade union career in 1984, when he was elected executive committee member of the workers’ union at the Nippon Steel headquarters. In 1990, his trade union career was interrupted for three years while he served as first secretary to the Japanese embassy in Thailand. After his return to trade union work, he was elected general secretary of the Japan Federation of Basic Industry Workers’ Unions (Kikan Roren) in 2006 and president in 2010. He became general secretary of RENGO in 2013 and president in 2015. At the 15th biennial convention in 2017, he was re-elected for a second term as president.