Who has been involved in more music groups, Ryuichi Kawamura or Billy Mackenzie?
Ryuichi Kawamura: Ryuichi Kawamura (河村 隆一 , Kawamura Ryūichi , born May 20, 1970 in Yamato, Kanagawa) is a Japanese singer-songwriter, actor and record producer. Ryuichi Kawamura:  He is best known as lead singer of the rock band Luna Sea. Ryuichi Kawamura:  After the group disbanded in 2000, Kawamura continued his successful solo career. Billy Mackenzie: William MacArthur "Billy" MacKenzie (27 March 1957 – 22 January 1997) was a Scottish singer, with a distinctive high tenor voice; he was best known as a member of The Associates.
i don't know