Liar Game X serves as a direct bridge between the second season of the television drama and the concluding film, The Final Stage. Often referred to as a phantom episode, it functions as the tenth episode of the second season and follows immediately after the defeat of the primary antagonist, psychology professor Ryo Katsuragi.

The special episode focuses on the immediate aftermath of the semi-final round. Honest college student Nao Kanzaki and her partner, the genius ex-swindler Shinichi Akiyama, have successfully navigated another round of the psychological tournament where contestants must deceive each other to avoid a crushing debt. Having won their battles but still trapped within the organization's system, they are now presented with the choice to enter the final stage of the Liar Game.

This narrative arc serves as a critical turning point, explaining the protagonists' motivation to voluntarily continue participating. Rather than introducing a new complex game, Liar Game X centers on the characters' internal conflict and strategic decision-making. Nao, who consistently believes in mutual trust and victory without harming others, must reconcile her ideals with the reality that the only way to truly end the game and free all remaining players is to confront the organizers directly. Akiyama, possessing the intellectual prowess to dismantle the game's mechanisms, supports this path. The episode sets the stage for the movie by confirming their joint resolve to enter the final round, aiming not just to win their own freedom but to expose and dismantle the entire corrupt organization that profits from human greed and desperation. It acts as a crucial character-driven prelude, shifting the focus from surviving individual matches to launching an offensive against the game masters themselves.