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According to original South Korean rules, the guest artist eliminates mystery singers at the end of each round, with the last remaining mystery singer ended up in a duet performance by one of the guest artists.
If the singer is good, he/she will perform again in an encore concert; if the singer is bad, he/she wins 1,000,000៛.
Rounds
Evidence round
The guest artist is given some time to observe and examine each mystery singer based on their appearance. Afterward, a muted video of each mystery singer that reveals only 0.3 seconds of their singing voice is played as an additional hint.
Introduction round
Each mystery singer introduces to the guest artist and panelists with its own voice. Good singers are telling the truth, while bad singers are allowed to lie.
Lip sync round
Each mystery singer performs a lip sync to a song; good singers mime to a recording of their own, while bad singers mime to a recording by someone else.
Talent round
The guest artist must describe one of the mystery singer's other talents, except "singing" itself. This may not be related to the "stage of truth", but depends on their identity.
For the returning guest artists (which also include foreigners or former good singers), names are displayed in italics.
For this season's highlights:
As part of the show's involvement by Oppo for sponsorship reasons, an encore concert (subtitled Special Concert) featured returning guest artist Zono, as well as brand ambassadors Pich Sophea and Step.