The story is set in the prestigious private school Hyakkaou Gakuen where its students' hierarchy are decided by how well they gamble. The victors will be able to get control over others while the losers will be subjected to harsh treatment and lose their money. Jabara Yumeko (Hamabe) is a new transfer student at Hyakkaou who looks pure and innocent on the surface but is actually someone who relishes in the thrill of taking on risks through gambling. As a result of her sharp observation powers and memory, she disrupts the hierarchy within the school as she overcomes the challengers sent by the student council to defeat her and drives them to destruction. Takasugi Mahiro plays a student in Hyakkaou named Suzui Ryota who is meek and doesn't have any talent to speak of. As such, he is at the lowest end of the hierarchy for domestic animals known as Pochi. When Yumeko transfers to the school, Ryota becomes her partner and is saved from his terrible fate in school thanks to her presence. He is also the only person who is not caught by the madness engulfing the students who are obsessed with gambling.
Morikawa plays Yumeko's rival Saotome Meari who later becomes her ally. Meari behaves over-bearingly towards others and is the top gambler in her class Year 2 Hana. She is the one who defeats Suzui and gives him his Pochi tag and takes on Yumeko when she just transfers to their school. Morikawa said that she had watched the anime version of "Kakegurui" and said that Meari is a very expressive person with a lot of exaggerated facial expressions. As such, she expressed her worry as to whether she could manage to do this because she had used up so much energy just on the first day of filming.