The elevator in Queen Decim opens to reveal a man and a woman who turn out to be a married couple. They mysteriously find themselves in an unknown bar without remembering anything else aside from their memory about their honeymoon trip. They are welcomed by a bartender named Decim, who explains their current circumstances. According to him, the couple has to stake their lives on a game which will be decided by the roulette, and they cannot leave the bar unless it is over. Upon hearing the absurd rules, the two try to find a way out of the bar, but to no avail. The bartender shows them a stack of corpses hanging behind a glass room, implying what will happen to them if they refuse to play the game. Without any other options, the couple presses the button and the roulette selects the game that they have to play.
That instant, the bar gets altered and two big dartboards are displayed in front of the couple where each of them will take turns in playing until one of them is down to zero point. The targets on the board have regions of the bodies inscribed on them, which are linked to the players’ nerves. Hence, the two of them will feel pain where the dart is thrown, and the greater the score is, the greater pain the pain will be.
At first, the two were skeptical about the game, but as they progress, they realize that what Decim told them is real. As Takashi confronts the bartender, he is given a hint that they can just intentionally miss the target. Just when they only have two more darts left, the two them “inadvertently” hit the targets, causing pain for both for them. Takashi, who seems angered when Machiko strikes his eye, is about to throw his dart when his wife begged him not to hit at least her belly. It is then revealed that she is 10 weeks pregnant, which makes Takashi regain his composure. But as he is about to throw the dart, a sudden flash of memory causes him to jolt and the dart hits the region of Machiko’s belly.
The two of them quarrel, and Takashi seems to remember how he found out that Machiko was having an affair when he overheard her friends talking on the day of their wedding ceremony. Machiko denies it, and as they argue, her memories return, and the dart that she throws unsteadily pierces Takashi’s heart, causing him to cough up some blood. Decim declares Machiko as the winner, but Takashi attempts to continue the game. That is when she informs her husband that there is no use continuing it, since having her memories back makes her realize that they are already dead.
As the bartender explains the existence of Queen Decim, Takashi suddenly has a vision of his final moments with Machiko before they plunge to their death. Convinced that his wife cheated on him, Takashi seems deranged as he refuses to accept their child and reviles his wife. Machiko is extremely shocked at her husband’s behavior, as if the man in front of her is different from the guy she married. She walks away from him and snickers at him as she affirms his suspicions.
Takashi completely loses his mind as he runs towards her with darts in his hand, ready to strike her. However, Decim, the arbiter, stops him with his strings until he loses his consciousness. He motions Machiko back to the elevator as he carries Takashi inside it where the two of them will be sent to their respective destinations.