The Kakegurui anime is a study of the human psyche in terms of hierarchy, risk-taking, ambition, trust and far more. In a way, its two main characters are like Batman and the Joker from Christopher Nolan's The Dark Knight -- a clash of order vs chaos. In this case, however, the Joker wins while Batman shows his true nature.
Kakegurui is set at an unusual private high school named Hyakkou Academy, where the sons and daughters of the wealthy elite learn to gamble, study the psychology of their opponents and evaluate risks. It's a delicate, hierarchy-based system that student Mary Saotome faithfully subscribed to -- until the chaotic Yumeko Jabami arrived.
How Yumeko Upended Hyakkou's System With Chaos & Instinct
Despite being the heroine of Kakagurui, very little of Yumeko's backstory or motivation is known, aside from her intense desire to gamble with the highest odds and experience the thrill of not knowing how a game of chance will turn out. She is driven almost entirely by instinct and the pursuit of pleasure, not ambition, making her a rough analog to Heath Ledger's version of the Joker. It is not entirely clear why the Joker does what he does, or what his backstory may be. To keep audiences guessing, he changes the story of his facial scars more than once, suggesting it doesn't matter or that he enjoys the confusion. Yumeko's history in Kakegurui is similarly mysterious. Like the Joker, she is defined by her whimsical and anarchic view on life, dedicated to tearing down the system rather than integrating herself into it.
Furthermore, the Joker believes all people are animals on the inside, driven by instinct and short-term desire, and such things as laws, politics, social hierarchy and even societal norms are just a self-serving facade. He was determined to forcefully expose the core nature of humanity and reveal the monsters underneath, and Yumeko is doing something similar at Hyakkou. She doesn't just reject the school's rigid rules and hierarchy -- she spites it all and draws out the wild, animalistic side of everyone she faces. In fact, Yumeko encourages her opponents to go wild and give in to their instincts, joining her in the revelry that exists outside the Academy's superficial system.
When Kakegurui began, Yumeko was content to pursue her own gambling-based pleasures alone, but she soon made two allies: Ryota Suzui and Mary Saotome. The former is a meek ally and friend, but the latter is more eager to convert to Yumeko's ways. Mary loved the system -- until Yumeko showed her an alternative.
Mary Saotome Realized Hyakkou's System Is Bogus
Mary may not be the paragon of virtue and justice like Batman, but before meeting Yumeko, she subscribed faithfully to Hyakkou's rules as a meticulous schemer who didn't favor chaos at all. She derived pleasure from making use of the school's brutal "housepet" system, and when Yumeko came along, Mary intended to humiliate her and make her into another servant. However, Mary lost to the newcomer's wild, carefree gambling methods, and began to think Yumeko's approach may be superior.
Kakegurui is a story where the Joker wins, convincing a member inside the system that it is not truly worthwhile. Mary, in awe of Yumeko's gleeful chaos and impulses, while envying her capacity to find pleasure in risk-taking and uncertainty, agreed to become her ally and friendly rival. She learned to detest the school council and housepet system, decrying it all as tyranny. She's not wrong -- the student council president, Kirari Momobami, sees the school as a fish tank for her own amusement, and only through chaotic defiance of the rules can Mary break free. If the system is shattered and everyone's true nature is exposed, then all students are on equal ground once again -- and that gives Yumeko and Mary a fighting chance to defeat it.