Doubt Poker

Doubt Poker
Gamble name
Japanese	ダウトポーカー
Translation	Dauto pookaa
Information
Chapters	The Merry-Making Girl The Manipulative Girl The Conflicted Girl The Probing Girl
Episodes	Episode 6 - Ongoing
Game
Players	Sachiko Juraku vs. Haruto Kibashira, Mamoru Kuonji, Nobuya Sera and Ren Kochi, Sachiko Juraku vs. Mary Saotome
Dealer	Tsuzura Hanatemari

Doubt Poker (ダウトポーカー) is a game invented by Mary Saotome in Kakegurui Twin for her gambling den. Mary, Tsuzura Hanatemari and Yukimi Togakushi work exclusively as dealers while wearing maid outfits. Various characters play Doubt Poker, including Kanade Musubi's group of friends and Jun Kiwatari who makes a cameo.

Later, Sachiko Juraku joins them and plays against Haruto Kibashira, Mamoru Kuonji, Nobuya Sera and Ren Kochi. 

Rules

Doubt Poker follows the same basic ruleset of Poker. Each player is dealt 5 cards and allowed to exchange (face-down) any number of cards once. Players then Bet, Raise, Fold or Call. However, after each player's hand is set:

• Players must announce their hands (e.g., "Three 4s") — they can either be truthful or lie about the cards in their hand.
• Players can now "doubt". From the dealer forward, by paying the current bet a second time, a player can force another to reveal their hand.

Showdown begins:

• Players who were not doubted play with their cards face down and the value they announced.
• Players who were doubted reveal their hands.
  • Doubt Fails (Truthful Players): Play with their hands revealed.
  • Doubt Suceeds (Lying Players): Immediately lose regardless of their hands.

The remaining player with the best hand, either revealed or annouced, is the winner. 

Game

Juraku joins Doubt Poker and intially plays against Haruto, Mamoru, Nobuya and Ren. When Ren raises ¥500000, everyone but Sachiko folds. In the doubting phase, against the odds of her chances of winning, Sachiko successfully doubts Ren, forcing him to reveal a false hand and into an instant loss. They play more matches against each other, but she remains the sole winner which results in the group leaving the den. Sachiko then asks other students to play with her, but everyone is too scared to even attempt.

In the absence of other players and knowing Juraku wouldn't leave until she is faced by her, Mary is forced to play against Sachiko  with ¥5000000 at stake and no end until one of them wipes out entirely. 

Juraku in shock after her first doubt fails.

The first round begins with Mary making a high bet of ¥1000000. In the annouce phase, Juraku annouces that she has 3 Queens while Mary annouces a full house. In the following doubt phase, only Juraku doubts. However, much to her astonishment, after Mary's hand is revealed to be true, her doubt fails and she loses. 

The second round starts with Juraku raising to a high of ¥510000. Mary then annouces a pair of 7s, followed by Juraku annoucing a pair of 10s. In the doubt phase, Juraku passes while Mary does and succeeds, successfully revealing a pig hand. Unlike the first hand's astonishment, Juraku begins to smirk now understanding the gist of Mary's gameplay. 

In the third round, Mary pushes the bet to another ¥1000000, however Juraku almost immediately calls her out for a pig hand. Despite this, Mary pushes through revealing a 10 high card, which Juraku doesn't doubt. In response, Mary doubts Juraku's annouced Pair of Queens. The doubt fails and Juraku wins the round. 

Mary unable to rationalize Juraku's accuracy.

Several more games continue, including a moment in which Mary believes Juraku is cheating due to the combination of Kurumi Kurume's advice and Jurakus extreme accuracy, however she is ultimately proved wrong. The game eventually ends with Mary having not only lost her initial ¥5000000, but an additional ¥5000000 loaned to her gamble by Full-Bloom.