Fudebakudo is a secretive martial art with ancient roots. Although Fudebakudo can be regarded as a rich combination of many martial arts, it has at its core a complex system of pen strokes based primarily on movements of the sword.

Fudebakudo (pronounced food-eh-back-ooh-d'oh) is the Japanese term for the art, and is usually translated as "The Way of the Exploding Pen."

This is the official Fudebakudo website.
There is also a book.