Born the son of Shunji Sakai, a famous comedian in Japan, Sakai initially came to fame by fronting the group sounds band The Spiders. This group, formed in 1962, was popular throughout the 1960s; they spawned several hit songs as well as thirteen situation comedy films featuring their music.

He took the title role of Songoku (Monkey) in the 1970s Japanese TV program Saiyūki. This gained him fame in many English-speaking countries in the early 1980s when it was dubbed by the BBC and retitled Monkey. Due to his fame playing the mythical character Songoku, Sakai created a dance called "the Monkey" which became a craze in Japan. Sakai went on to a successful solo career after The Spiders disbanded, and continued acting in films and on television.