Yumeko Jabami, a second-year transfer student at Hyakkaou Private Academy, enters a world where social dominance hinges on gambling prowess. Born into the gambling-specialized Jabami branch of the Momobami clan, she was orphaned young in a suspected car accident and raised alongside her sister Souko by their aunt Tsugiko. At six, Yumeko usurped Tsugiko’s bid for family control in a dice game, fueled not by ambition but an insatiable hunger for the gamble’s adrenaline. Her lifelong addiction stems from a philosophy that life’s core lies in staking everything on uncertainty. She gambles for the visceral rush of risk, indifferent to material outcomes, embracing chance as liberation. Though she feels no remorse for defeated opponents, she recognizes her own inability to share their anguish. At Hyakkaou, Yumeko shatters the academy’s corrupt hierarchy, dismantling systemic cheating through cunning and perception. She unravels Mary Saotome’s rigged rock-paper-scissors strategy, deciphers Itsuki Sumeragi’s card patterns, and counters Yuriko Nishinotouin’s sword-assisted deception. Each victory underscores her tactical brilliance masked by a playful demeanor. Her fixation on challenging student council president Kirari Momobami leads her to temporarily accept demeaning "housepet" status after a tactical loss to Yuriko, exploiting the role to secure future high-stakes matches. Beneath her charismatic cheer lies a calculating mind, her eyes flaring crimson during manic surges of gambling euphoria. Linked to the Momobami’s "Hundred Devouring Families" through her surname’s kanji, Yumeko wields financial independence from an inheritance, funding her hospitalized sister’s care while bankrolling her own schemes. She shields allies like Ryota Suzui and Mary Saotome from harm, orchestrating scenarios to empower them—such as freeing Mary from debt through collaborative trickery. Spin-offs like *Kakegurui Twin* and *Kakegurui Midari* echo her influence, though her core remains unaltered: a chaos-seeker who condemns gambling for selfish gain or self-destruction. Live-action adaptations preserve her thrill-driven essence while softening overt sensuality. She frames gambling as a pact of mutual risk, demanding total surrender to uncertainty—a creed she follows relentlessly, undeterred by ruin, accepting loss as the gamble’s inevitable price.