Premise: Kenichi Hagiwara (萩原健一; "Hagiwara Ken'ichi", born 26 July 1950 in Omiya, Saitama, Japan), also known as Sho-Ken, was the lead singer of The Tempters , the "bad boys" of the Group Sounds Japan pop scene in the mid and late 1960s. A teen idol with a legion of loyal fans, Hagiwara was known for his good looks and arrogance, which appealed to both young male and female Japanese fans.
Hypothesis: The Group Sounds Japan pop scene peaked in popularity in the 1960's.