Keikichi Usui
At the invitation of Hiroshi Koshikawa, he participated in the formation of "Robin Hood". In April 1969, he left the band. Usui started solo career under his stage name "Kei Aoyama" (青山啓, Aoyama Kei). The following year, in September 1970, he made his solo debut with "Mr. Sex's Holiday" written by Kuranosuke Hamaguchi.