The Unique Rule (ユ二ークのルール, Yunīku no Rūru) is a rule in the Genso Suikoden Card Stories TCG that restricts the cards you can play.
Overview
In its most basic form, the Unique Rule states that only a single character card of a name can be deployed at any one time by either player. It represents the idea that each character is a unique individual in the world.
Each player cannot deploy a character card of the same name, nor can a single player play two cards of the same name. This does not restrict the deck, which can contain any number of cards of the same name (Genso Suikoden Card Stories TCG)/4 cards of the same name (Genso Suikoden Card Stories TCG Chapter II), merely what can be played on the field.
The rule encompasses different numbered cards with the same name. So a later edition card cannot be played alongside an earlier release of the same card, even if their attributes and abilities differ. It also applies to cards with multiple names in them. For example, there cannot be a McDohl & Germio card and a McDohl card, or a Gremio card, on the game field simultaneously.
The rule also applies to Mastermind cards. You may not have a Mastermind card and a regular Character card of the same name in play. If your opponent plays a Mastermind card, you cannot play a Character card of the same name either.
If a card that would break the Unique Rule is deployed by an effect, it is immediately discarded. The Unique Rule does not apply to mission cards or facilities cards as they are not character cards.
The Betrayal conditional takes advantage of the Unique Rule by replacing a character card with the Betrayal conditional your opponent has on the field with the version you played, forcing the original card to be discarded.