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, 17 March 2010
I have "Kuroiban Compound" face down after use it Open action in play. ("Open: Turn this card face down: Until it leaves play or is turned face up, this card is a Ninja Personality with 2F, 3C, an Honor Requirement of "-", Gold cost of 4, and Personal Honor of 0. If turned face up, it returns to your home bowed as a Holding." ) in play.
I play Mysterious Deaths (Unique Kolat Limited: Lose 4 Honor. Destroy each player's lowest Gold Cost unit. If any player has more than one unit tied for lowest Gold Cost, he choses which of his units is destroyed. Remove this card from the game.). My lowest Gold Cost unit is "Kuroiban Compound" Ninjitsu Ninja (4 Gold Cost).
I choose "Kuroiban Compound" and use it Ninjitsu Reaction (Any number of times per turn, after an action targets a facedown Ninjutsu Personality you control, pay Gold equal to his Ninjutsu value: Turn the Personality face-up. If he is now an illegal target for the action, negate its effects on him.) so :
A. My Kuroiban Compound will be destroyed B. My Kuroiban Compound will negate destruction on it, but I need choose other lowest gold cost personality C. My Kuroiban Compound negate destruction on it.
Brook Cunningham (rules official), 17 March 2010
I have "Kuroiban Compound" face down after use it Open action in play. ("Open: Turn this card face down: Until it leaves play or is turned face up, this card is a Ninja Personality with 2F, 3C, an Honor Requirement of "-", Gold cost of 4, and Personal Honor of 0. If turned face up, it returns to your home bowed as a Holding." ) in play.
I play Mysterious Deaths (Unique Kolat Limited: Lose 4 Honor. Destroy each player's lowest Gold Cost unit. If any player has more than one unit tied for lowest Gold Cost, he choses which of his units is destroyed. Remove this card from the game.). My lowest Gold Cost unit is "Kuroiban Compound" Ninjitsu Ninja (4 Gold Cost).
I choose "Kuroiban Compound" and use it Ninjitsu Reaction (Any number of times per turn, after an action targets a facedown Ninjutsu Personality you control, pay Gold equal to his Ninjutsu value: Turn the Personality face-up. If he is now an illegal target for the action, negate its effects on him.) so :
A. My Kuroiban Compound will be destroyed B. My Kuroiban Compound will negate destruction on it, but I need choose other lowest gold cost personality C. My Kuroiban Compound negate destruction on it.
Mysterious Deaths doesn't target, so you can not use the Ninjutsu Reaction in response to it. Therefore:
A. My Kuroiban Compound will be destroyed
However, there is good news. When the Kuroiban Compound turns face-up in the discard pile from having been destroyed as a Personality, the final delayed effect of its ability will trigger and return it to play bowed. Hurray!