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, 22 February 2008
You Die With Me: Heroic Reaction: After another player resolves a Battle action which destroyed one of your Hero Personalities: Destroy a target Follower, or Personality without Followers, in the current enemy army. Chuda Hankyu: Battle: Destroy this card and dishonor this Personality: Lose 3 Honor. Destroy a target Follower, or Personality without Followers, with a Force less than 5 at any location.
I attack and opponent defends on another province(opposed or unopposed) or he desides not to defend at all. I use Chuda Hankyu action and destroy one of his Heros (home or another battlefield). 1. Can he use reaction od You Die With Me to destroy me personality at a battlefield where I'm attacking and resolving battle actions (he got no personality there)? 2. If he would be opposed in the another battlefield - can he use reaction on You Die With Me to destroy one of my personalities there? The battlefield hasn't been resolved yet. 3. If he would be able to play Misdirection can he chose to destroy on of my own personalities at any location?
Martin Lund (rules official), 26 February 2008
You Die With Me: Heroic Reaction: After another player resolves a Battle action which destroyed one of your Hero Personalities: Destroy a target Follower, or Personality without Followers, in the current enemy army. Chuda Hankyu: Battle: Destroy this card and dishonor this Personality: Lose 3 Honor. Destroy a target Follower, or Personality without Followers, with a Force less than 5 at any location.
I attack and opponent defends on another province(opposed or unopposed) or he desides not to defend at all. I use Chuda Hankyu action and destroy one of his Heros (home or another battlefield). 1. Can he use reaction od You Die With Me to destroy me personality at a battlefield where I'm attacking and resolving battle actions (he got no personality there)? 2. If he would be opposed in the another battlefield - can he use reaction on You Die With Me to destroy one of my personalities there? The battlefield hasn't been resolved yet. 3. If he would be able to play Misdirection can he chose to destroy on of my own personalities at any location?
Neither the Rule of Presence nor the Rule of Location apply to Reactions, only Battle Actions - as noted in their text.
"Destroy a target Follower, or Personality without Followers, in the current enemy army." is very explicit. You can only target cards in the "current enemy army," - the enemy army at the Current Battlefield.
Finally, yes, he could play Misdirection to force you to kill one of your own cards at any location with Chuda Hankyu. You are actually allowed to kill your own cards with the Hankyu - it is not a Ranged Attack thus isn't restricted anywhere in the rules to only working on "enemy" cards.