Two years have passed since Round 3 of the Liar Game. Nao Kanzaki has returned to her normal life, now with the new friends she made from the Game, and Shinichi Akiyama has gone overseas. However, the Liar Game has yet to end, as the two encounter letters detailing Round 4's location and rules: a 3v3 battle between the "Kingdom of Sun" and the "Kingdom of Moon" in an abandoned old arcade. Nao is convinced to re-enter the game by Tanimura, who says that only her pure nature can save the other players, and Akiyama returns to find out more about the truth behind the Game. Joining their team is former archenemy Yuji Fukunaga, and they have to work together as vanguard, main body and general in individual games to earn more chips than the other team, with every player having 150 chips each amounting to 1 million yen. The first vanguard battle, with Fukunaga against a Yuichi Nishida, is 24-round russian roulette with the sound of bullets simulating "death", and the loser has to pay the winner 50 million yen. Meanwhile, an ominous player and former psychology classmate of Akiyama's — now a professional university lecturer — by the name of Ryō Katsuragi arrives to participate in Round 4 in a different venue.