This question is about how Crossing the Forbidden Sea, Yoritomo Eihiko, and Ambush interact.
If Crossing the Forbidden Sea is in effect and an opponent plays Ambush or Silent Struggle targeting my personality, may I react to the targeting (with say, Deflection, Chugo Seido, or Final Sacrifice) to redirect the card to a 7 or 8 cost unit, then react to my own reaction with Eihiko to force my personality to not assign?
Crossing the Forbidden Sea Until your next turn begins, units with a total Gold Cost of 6 or less may not be assigned to battlefields.
Ambush Limited: Target your unbowed Personality: Create a battlefield (not at any province). Assign your Personality's unit to attack there. Assign another player’s target unit to defend there, even if its Personality is bowed. Other units will not move there. Fight a battle there (after this action's resolution). After the battle ends, lose 5 Honor.
Silent Struggle Ninja Limited: Choose your performing unbowed Ninja Personality: Create a battlefield (not at any province). Only Ninja Personalities will move to it or from it. Assign your Ninja 's unit to attack there. Assign another player's target unit to defend there, even if it's Personality is bowed. Fight a battle there (after this action's resolution). After the battle ends, lose 5 Honor.
Yoritomo Eihiko Mantis Clan • Magistrate • Extortionist Reaction: After you announce an action: Reduce the Gold Cost of a target card (in play) by 2 until the action ends.