Reaction:
Before your target Personality enters a duel, bow him and choose your performing unbowed Samurai at the same location: Your Samurai enters the duel instead. Bow him after the duel ends.
Duels in Rokugan are ritualized. The challenge, the terms, and the ceremony are all subject to centuries of tradition. One tradition is the privilege of having another to stand in the place of the challenged, when circumstances are right.