Mary Saotome is a second-year scholarship student at Hyakkaou Private Academy, originating from a non-wealthy family. Her parents encouraged her to befriend affluent students, fueling her early drive for social advancement and financial success within the school's hierarchy. She stands at average height with long blonde hair in twin ponytails secured by black ribbons and dark-yellow eyes. Mary wears the standard Hyakkaou uniform: a red blazer with black trim and gold buttons, a white button-up shirt, black tie, gray pleated skirt, black socks or stockings, and brown loafers, typically with natural makeup including mascara, blush, and pinkish-beige lipstick. Initially, Mary displays a sadistic, egotistical personality, cruelly taunting opponents during gambles and exhibiting extreme confidence, particularly toward those with lower status like housepets. Her treatment of Ryota Suzui—forcing him into servitude over a debt—exemplifies this ruthlessness. However, after losing to Yumeko Jabami and being demoted to housepet status herself, Mary suffers significant humiliation, culminating in a mental breakdown during a match against Yuriko Nishinotouin. This erodes her pride and arrogance. Upon regaining status, she becomes less overtly cruel, though easily nettled by Ryota's timidity or Yumeko's recklessness. She develops a deep-seated hatred for the student council and the housepet system, vowing to make them pay for dehumanizing students. The spin-off *Kakegurui Twin*, set before the main series, reveals a softer side. Shortly after transferring, Mary reunites with Tsuzura Hanatemari, a former classmate now a bullied housepet labeled "Mittens." Tsuzura's plight fuels Mary's disdain for the caste system. Though initially leveraging Tsuzura's financial help strategically, Mary genuinely pities her and forms a protective bond. This friendship drives Mary to prioritize ending Tsuzura's housepet status. She later befriends Yukimi Togakushi after winning her library gambling den, allowing Yukimi to remain under her supervision. These alliances highlight Mary's capacity for loyalty and empathy. Mary's gambling prowess stems from sharp intelligence, an aptitude for calculated risks and cheating, and strategic alliance-building. She excels at probability calculations and adapts quickly to game mechanics, though she often loses initial rounds by underestimating opponents' cheating. Her reliance on allies like Tsuzura and Yukimi proves critical in high-stakes matches, such as the couples' dating game and scavenger hunt, where collaboration secures victories. Despite overtures from influential figures like Student Council Treasurer Aoi Mibuomi—seeking her help to overthrow President Sachiko Juraku—Mary refuses subordination, preferring to manipulate power structures while maintaining independence. In the main series, Mary reluctantly partners with fellow housepet Yumeko Jabami during the Debt Settlement game, devising a card-switching strategy that clears both their debts. Yumeko declares them friends, and Mary gradually warms to her despite exasperation at her risk-taking. Mary later declines an invitation to join the student council from President Kirari Momobami, condemning the housepet system and rejecting Kirari's hypocrisy. Her resolve strengthens during the school election arc, where she aids Yumeko and Ryota in the Nym Type Zero game. By deducing Runa Yomozuki's shuffling pattern, she directs Ryota to reveal his cards, outmaneuvering opponents and whispering her ambition to become academy president. Her dynamic with Vice-President Ririka Momobami evolves from annoyance to mutual respect; after a forced partnership to save Yumeko from poisoning, Mary challenges Ririka to gamble independently of Kirari's influence, fostering trust that culminates in Ririka removing her mask in Mary's presence. Mary's character arc reflects a journey from isolated ambition to camaraderie, underpinned by resilience against setbacks, strategic ingenuity, and an unwavering rejection of systemic oppression. Her relationships—particularly with Tsuzura, Yukimi, Yumeko, and Ririka—catalyze her evolution from a self-serving opportunist to a principled gambler invested in collective dignity.