A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from the Wayback Machine (its copy), so posts 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, 8 November 2006
Can Tiger´s Mouth bow Hida Kuon if he performs an action targeting the personalities who belong to the player who played Tiger´s Mouth?
Hida Kuon: Crab Clan Samurai · Clan Champion · Berserker · Hero · Yu 10 · Experienced 4 · Unique · Loyal · The Jade Crab. Other players' card effects may not bow Hero Personalities at Kuon's location. Each other player must discard a card as a cost the first time each phase he targets a Personality you control. Battle: Target a unit with less Force than this unit. Bow it.
Tiger´s Mouth: Center Formation Formed by 3 Personalities with at least 5 Force each. Other players actions targeting your units have the additional cost of bowing a Personality the player controls at this battlefield
Zen Faulkes (rules official), 8 November 2006
Can Tiger´s Mouth bow Hida Kuon (Experienced 4) if he performs an action targeting the personalities who belong to the player who played Tiger´s Mouth?
Tiger's Mouth creates an additional cost. The Experienced 4 Kuon's trait does not concern costs (it only cares about "Other players' card effects"), so you must meet the additional cost of the action.
To put it another way: Tiger's Mouth doesn't bow cards. It increases costs.