The Mystery Inc. gang travel to Japan for Daphne's martial arts tournament, and stumble upon the mystery of the Black Samurai. The only way to defeat him is by solving riddles and fighting ninjas, and the ones you'd least expect to end up saving the day.
Scooby-Doo and the Samurai Sword
The Mystery Inc. crew travels the globe on a transcontinental treasure hunt to solve a series of ancient riddles. Scooby-Doo and Shaggy are indoctrinated by an unlikely Sword Master.