Born in Tokyo, Usami was educated at the Takachiho College of Economics.
In 1946, he began working at the Fuji Cotton Spinning Company.
Later in the year, he moved to work full-time for the new Japan Federation of Textile Workers' Unions.
He served on the union's Central Executive Committee from 1947, became Assistant General Secretary in 1955, General Secretary in 1961, and President in 1971.
The same year, he was elected as president of the ICFTU Asia and Pacific Regional Organisation.