Oichi, the blind swordswoman, receives a scroll with a secret message from a dying courier, that must be handed to Murobuse, a high officer of the Shogunate. Her path is full of obstacles that delay her, or put her life in danger, from hungry orphans to a dagger thrower in a carnival, from robbers to a rival samurai… Will the secret of how to produce a new kind of explosive fall in the wrong hands?