ごく普通の家庭に生まれた少女、早乙女芽亜里（森川葵）は私立百花王学園への編入初日、期待に胸を躍らせていた。なぜならそこは、政財界の子女が多数集う正真正銘のお金持ち学校。憧れのお嬢様ライフがいよいよ今日からスタートするからだ。1年華組の歓迎ムードに気をよくする芽亜里だったが、クラスの中心人物、愛浦心（福本莉子）からあることに誘われる。それは‘ギャンブル’。そう、この学園では、勉強やスポーツの成績は評価されず、最も重要なのはギャンブルの強さだった。はじめて挑んだギャンブル「時短大富豪」で洗礼を浴び、惨敗する芽亜里。一度は逃げ出すが、かつての同級生、花手毬つづら（秋田汐梨）との出会いで彼女は活路を見出す。こうして、早乙女芽亜里のギャンブルロードが始まるのだった-。
겜블이 모든 것을 좌우하는 햣카오학원에 들어온 사오토메 메아리. 처음 겪은 갬블에서 참패한 메아리에게 초등학교 시절의 친구 츠즈라가 다가온다.
Born into an ordinary family, Mary Saotome is thrilled on her first day transferring to Hyakkaou Private Academy. This is no ordinary school—it's a prestigious institution attended by the children of political and business elites, where Mary's dream of living a refined, elegant life is about to begin. Welcomed warmly by her new classmates in Hana Class 1, Mary feels optimistic. However, the class's central figure, Kokoro Aiura, invites her to participate in something unexpected: gambling. At this academy, academic or athletic achievements mean nothing—gambling prowess reigns supreme. Mary's first taste of gambling in a game called "Speed President" ends in a crushing defeat. Though she initially tries to escape, an encounter with her former classmate, Tsuzura Hanatemari, sparks a new resolve. Thus begins Mary Saotome's journey down the path of gambling.
