A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
A player, 23 January 2012
*Dragon's Breath Castle After another player's Dynasty Phase begins, if he controls any Personalities and he assigned none of them to an attacking army this turn: Gain 2 Honor. Reaction: Even if this card is bowed, after engaging at a battlefield at one of your provinces: The Attacker targets and bows one of his Personalities there.
*Know No Fear Reaction: After another player's action targets your performing Samurai: Negate his bowing and movement from the action's effects. Reaction: After a Fear action targets your performing Samurai: Negate its effects.
Question: Could you play Know no Fear to negate the Reaction of Dragon's Breath Castle? Need your insight Sirs.
Brook Cunningham (rules official), 23 January 2012
*Dragon's Breath Castle After another player's Dynasty Phase begins, if he controls any Personalities and he assigned none of them to an attacking army this turn: Gain 2 Honor. Reaction: Even if this card is bowed, after engaging at a battlefield at one of your provinces: The Attacker targets and bows one of his Personalities there.
*Know No Fear Reaction: After another player's action targets your performing Samurai: Negate his bowing and movement from the action's effects. Reaction: After a Fear action targets your performing Samurai: Negate its effects.
Question: Could you play Know no Fear to negate the Reaction of Dragon's Breath Castle? Need your insight Sirs.
Yes, you can.
Though the attacker is doing the targeting for the Dragon's Breath Castle Reaction, it's still "another player's action" per Know No Fear's trigger.