Itsuki uses cards manufactured by her father's company, which feature tiny heat-sensitive patterns or "marks" on the back that only she can identify. This allows her to "see" the cards before they are flipped. Yumeko’s "Madness" Unleashed

Yumeko manipulates Itsuki into increasing the stakes, eventually betting 20 million yen.

The episode centers on a high-stakes game of a complex variation of the classic card game "Concentration." Unlike the standard version, this game uses two decks of cards, totaling 104 cards, making the odds of finding pairs significantly harder.

Itsuki Sumeragi , a first-year student and daughter of a wealthy toy manufacturer, challenges Yumeko . Itsuki is known for her extreme obsession—collecting the fingernails and toenails of those she defeats in gambling.