Premise: "King of the Jungle" is a song written and recorded by English girl group Bananarama. It was released as a single in Japan only from their self-titled second album in 1984. The song is the second single from Bananarama to be a Japanese-only release (following "He's Got Tact" in 1982).
Hypothesis: King of the Jungle was released as a Japanese-only realise because the group didn't think it would sell well outside of Japan.