Don't forget about the other guys dueling with Pink Lady during their amazing run in 1977-79... what about Chiharu Matsuyama, who scored #1 hits like "Kisetsu no naka de"? Or Takao Horiuchi, formerly of the group Alice, with his #1 song "Kimi no hitomi wa 10,000 Volt"?
Yes, I'm just trying to show off what I know about '70s J-Pop...