Born in the Kanagawa Prefecture in on April 20, 1949, Shin's birth name was Katsutaro Okamura (岡村勝太郎, "Okamura Katsutarō"). In 1964 at the age of 16, Shin joined The Play Five with Yukio Miya, which was created and became a lead vocalist. In 1967, when Yukio Miya and The Play Five changed their group name to "The Jaguars", they made their debut with "Want You See Again (君に会いたい, "Kiminiaitai")" at .