狂きょう言げん回まわし

noun

supporting but indispensable role; major supporting role

Originally a kabuki term for a character who moves the plot forward while appearing secondary; now used broadly for a person or element that is not the main focus but is essential to the story or outcome.

• 彼かれは主しゅ役やくではないが、狂きょう言げん回まわしとして物もの語がたりを動うごかしている。

  He's not the lead, but as a major supporting role he drives the story forward.

• この事じ件けんの狂きょう言げん回まわしは、意い外がいな人じん物ぶつだった。

  The unexpected person turned out to be the one pulling the strings behind this incident.