One day, Naho Takamiya receives a letter written to herself from ten years in the future. As Naho reads on, the letter recites the exact events of the day, including the transfer of a new student into her class named Kakeru Naruse. The Naho from ten years later repeatedly states that she has many regrets, and she wants to fix these by making sure the Naho from the past can make the right decisions—especially regarding Kakeru. What's more shocking is that she discovers that ten years later, Kakeru will no longer be with them. Future Naho asks her to watch over him closely.

Run by a corrupt and sadistic school council, the “system” at Hyakkaou is based on gambling, with losers who cannot cover their debts being demeaned by their peers and forced to serve their debtholders. And if that’s not terrifying enough, some games can result in losing an eye, one’s fingernails, or even their life! But the system is shocked when transfer student Yumeko Jabami arrives. Dark, mysterious and attractive, she’s a wildcard who plays for the thrill of it…

In order to save her brother and nephew who have been kidnapped by a mysterious religious group known as the Genuine Love Society, Juri and her family cast a spell using a stone hidden by her grandfather to enter the world of stopped time known as Stasis. However, when they infiltrate the kidnapper's base, they're met by other people who can also move about freely. With grotesque creatures lurking about, will they be able to escape the parallel world and return to their normal lives?!