Nao Kanzaki is honest to a fault. Uncorrupted and virtuous, Nao is the perfect target for a large-scale scheme—the so-called Liar Game. Suddenly in possession of one hundred million yen, she is expected to steal the same amount from her assigned opponent—her former middle school teacher—or face crushing debt. Trusting her teacher without question, Nao quickly realizes that she is trapped.

To gain an advantage, Nao comes in contact with Shinichi Akiyama, a brilliant con artist just released from prison. Though Akiyama has no real reason to help the naive girl, he ends up aiding her victory. However, driven by her unwavering sense of justice, Nao chooses to continue into the next round, and Akiyama, unwilling to leave her to fail, joins her. In the Liar Game, participants are expected and required to deceive, manipulate, and betray or be buried in lifelong debt. Yet Nao, with the help of Akiyama's genius, is determined to beat the game without abandoning her morals and prove that generosity and sincerity will always prevail.