Itsuki Sumeragi is a supporting character in Kakegurui. She's a first-year student belonging to the "flower" class at Hyakkaou Private Academy and a member of the Student Council. Her father is the president of a prominent toy company in Japan.
DesignShe wears the Hyakkaou Private Academy issued uniform; a red blazer with black trim around the cuffs and collar that is decorated with gold buttons, underneath she wears a white button up with a black tie as well as a pleated skirt with black stockings that have silver stars on the sides of them along with a pair of brown loafers with black soles. She has blue eyes and blonde hair that comes down to her chin and bangs that reach her eyebrows. She has a green hairband in her hair. She also has pink painted nails with star-like decorations on them. In the manga, her nails are decorated with the suit of clubs.
Itsuki uses her gambling skills as well as the daughter of the president of a toy company utilizes her wealth to her advantage in order to get whatever it is she desires, whether it be a seat within the student council or even her collection of painted human nails. Equally as manipulative as she is business savvy, Itsuki uses her gambling match against Yumeko Jabami to promote her family's latest product while hiding her own secret that the cards she uses are rigged with temperature-sensitive technology that leaves her undefeated at her own game until Yumeko uncovers the truth of her deception.
Kakegurui - Compulsive Gambler
Following Mary Saotome's defeat at the hands of Yumeko, the student council members hear about this news. One of which was a current member of the student council, Itsuki Sumeragi, who with her riches as the daughter of the largest toy company in Japan, got the position. Itsuki showed excitement in trying to gamble with Yumeko.
During lunch time, Itsuki immediately followed Yumeko's trail in the school and somehow managed to get to her. She invites her to gamble with her, and while Suzui tries to halt Yumeko from gambling, she still wanted to gamble and accepts Itsuki's gamble invite. She invites her to play a game of "Double Concentration" in which the rules are fairly simple. 2 decks of cards will be used, making the total card usage of each game 104. Each player must then flip 2 cards of their choice in their turn. If they flip a pair of matching cards with the same suit and number, then they gain 2 points and the flipped cards are remained flipped open. If they flip cards that don't exactly match, then they lose a turn to the opponent. For example: You get a pair of 9 of Hearts and 9 of Spades, then they don't count as a matching pair. But a matching pair would be 2 4 of Clubs or 2 6 of Diamonds. For their match, Itsuki places down 20 irregular colored chips which are worth 1 million yen each, making it a total of 20 million yen. For the betting, Itsuki uses all the 20 million worth chips, making their bet 20 million. Though Yumeko says she does not have the money, Itsuki assures her worries by saying she'll lend her 20 million.
Then, they begin the game of "Double Concentration". She wins the first round, even though both of them have a great memory. Yumeko really wants a second round but has no more money. So Itsuki suggests Yumekos nails as a bet. She shows them their nail collection, which she all got from people. She starts to act crazy. Yumeko accepts and Itsuki is sure, she will win, since there is a small mark on half of the cards, so she is unable to lose. However Yumeko caught up on the trick and beats her. As Yumeko suggests to rip Itsukis nails out, she cries. After this loss, she is expelled from the student council.
When Yumemi challenged Yumeko, Itsuki joined in to support her. But she only wanted to get back on the council. Later when Yumeko challenged Kaede, she was hoping thta Yumeko would win. But then she needed more money and turned to her. She was hesistant at first but decided to lend her money. The bets got higher and higher. Itsuki knew, that losing would mean, her life was practically over. Enraged she ripped off all of her nails and betted the amount of money her life was worth. After Yumeko ended up winning, she revealed, that the two were planning this whole act in order to lower Kaedes guard. She didnt get back on the council however.
Since Kaede betted his lifeplan Yumeko received it, but gave it to Itsuki. Its apparent, that she actually has feelings for him. She watches over him, as he lays in bed, still under shock. She goes on to collect quite a few votes during the election. And she is also present during Yumemis battle against Kawaru.
Since she now owns Kaedes lifeplan, she treats for him, but he just tells her to leave. She then mocks him, but secretly just wants to motivate him to get his spirit back. She is shocked to see when he also plays the Greater Good Game with her, Yumeko, Miroslava and Ibara. He says however that he doesnt care if he wins. She is annoyed at his lack of will for anything and tries to somehow cheer him up. Her romantic feelings are later revealed by Miroslava, who promised to keep them a secret at first.