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, 2 March 2010
Can I use the reaction off of Hiruma Gohachiro after my opponent plays Flanked by Nightmares. I would think it would be allowed since it's my opponents action. I don't think the fact that I'm targeting the person matter, but I wanted to make sure.
Relevant card text:
Hiruma Gohachiro Reaction: After another player's action targets another Personality in Gohachiro's army: Negate the Personality's destruction from the action's effects.
Flanked by Nightmares Battle: If your current army has more units than the current enemy army, bow your target Shadowlands Personality: The enemy leader targets and destroys a Personality in his current army.
Brook Cunningham (rules official), 2 March 2010
Can I use the reaction off of Hiruma Gohachiro after my opponent plays Flanked by Nightmares. I would think it would be allowed since it's my opponents action. I don't think the fact that I'm targeting the person matter, but I wanted to make sure.
Relevant card text:
Hiruma Gohachiro Reaction: After another player's action targets another Personality in Gohachiro's army: Negate the Personality's destruction from the action's effects.
Flanked by Nightmares Battle: If your current army has more units than the current enemy army, bow your target Shadowlands Personality: The enemy leader targets and destroys a Personality in his current army.
Yes, Gohachiro may react to being targeted by Flanked by Nightmares, for the reason you gave.