Japanese prodigy Naoya Inoue was a heavy favorite coming into the World Boxing Super Series bantamweight final on Thursday night.

The undefeated king known as “The Monster” won, but it was an unexpected struggle.

Inoue (19-0, 16 knockouts) defeated future Hall of Famer Nonito Donaire by a unanimous decision (116-111, 117-109, 114-113) before a jam-packed crowd at Saitama Super Arena.