The game is played in 3 rounds using a deck of Tarot cards. The cards are placed face-down on a table and the game is played by flipping them up one by one. Cards are assigned a score equal to their number i.e. The World being XXI is assigned 21 points. This score is awarded only to one of the players, with the outcome being dependant on the score. Cards score depending on their position when flipped up, if they are facing upwards they award positive points, if they are reversed they award a negative score. The sole exception to this rule is The Fool which serves as the game's "Joker". If The Fool is face up it is an instant-win for the score player, if reversed it is an instant loss. Both scenarios happen regardless of any score.
The loser is forbidden entry to Hyakkaou Private Academy permanently. For Yumeko this deprives her of her much beloved sanctuary of gambling. For Kirari it entitles the loss of the "aquarium" she worked so hard to build.
The game begins by assigning three different people who will each flip one card during their turn. As the game is played using Tarot, these individuals represent the Present, Past and Future respectively. Yumeko is selected as the score player with every card flipped counting only for her. If the total outcome is positive, she wins, if negative, she loses. Yumeko as the "Present" plays first and flips "The Magician - I" facing upwards, thus she earns one point.
Next is Kirari's turn as the "Past" who begins talking about fate. She flips her card and it is "The World - XXI" in reverse position, this Yumeko's score is -20, placing her on an extremely difficult spot. Mary Saotome and Itsuki Sumeragi protest that Kirari cheated but Runa silences both of them and guarantees no cheating was conducted. The next turn is given to Ryota Suzui who as the "Future" will flip the final card, but is conflicted and undecided. Yumeko encourages him to play as the risks and pain will be hers alone. Ryota protests this blurting that he will be troubled if she leaves, basically confessing to her on the spot.
But Mary and Itsuki notice a way to identify the cards but before they are able to say more, Runa demands them both to say nothing. Ryota however manages to learn that the cards can be distinguished and begins to pay attention. He notices one particular card that is marked, which is believed to be "The Fool" as it was the only card that Kirari had taken before the game started.
Ryota feels tempted to flip the card but at the last moment decides against it. He reasons that the card could in fact be "The Fool" and that the mark was set up by Kirari in order to ensure a risky game to occur. However he protests against Kirari setting the mood for herself and with uncharacteristic courage decides to gamble in his own terms. This great display of resolve fascinates Yumeko, exciting her. She then holds him from behind while happily letting fate guided by his hand to decide everything. She subsequently whispers into his ear to "Gamble" causing in Ryota a gambling impulse.
Ryota then selects his card and flips it up. He flips "The Judgement - XX" in upright position. Thus he scores 20 points for Yumeko, ending the game with a net 0 score, resulting in a draw.
Ryota narrates the rest stating how Yumeko changed the academy influencing several people in different ways, and how she is a thorough and through "Compulsive Gambler".