Rio and Dana follow her ferret, Chip, to a casino where the mysterious Joker is holding Howard captive. She challenges Rio to a game of blackjack in order for her to escape her Roll Ruler, which forces them into a draw at every play. As Rio realizes her compassionate ways made her ignorant of Rina's true feelings, she ends up losing a hand. However, after Mint and Jack arrive, Rio manages to win a hand, to which Joker presents with a Gate and frees her from her Roll Ruler, deeming her worthy of challenging Rina again. Meanwhile, Rina becomes curious of Cartia's motives for getting all the Gates. Later, Rio learns Dana is the final Gate Holder, who challenges her to cross a trap filled bridge in order to win her gate. Using her Roll Ruler, Rio figures out the positions of the traps and how to turn them against her, allowing her to win. As Howard converses with the true identity of Joker, Rio and her friends head to Goltschmidt Kingdom in order to confront Rina again.
リオとハワード、そしてダーナが迷い込んだ無人の繁華街――そこは「ジョーカー」を名乗る、謎の人物が作り出したロールルーラーの世界だった。ロールルーラーとは、相手の運気を操り、勝負の場を支配する能力。ジョーカーに勝負を挑まれたリオは、彼のロールルーラーに翻弄され、連敗してしまう……。そのとき、リオの脳裏にリナと過ごした幼少の頃の思い出が蘇る。
はたしてリオたちは、ジョーカーの世界から抜け出すことができるのか？
