The story takes place in a world with a group of people known as the “Immortals.” Immortality is not a blessing, but a supernatural phenomenon or genetic mutation called the “Eternal Shackles.” Immortals cannot die by ordinary means, but every time they “die,” they pay a price: they may permanently lose some of their core memories, or have certain emotions or personality traits intensified, gradually distorting their true selves. The world is home to a mysterious organization called the “Endgame Containment Facility,” which may be dedicated to studying, managing, and even trying to “cure” the Immortals. There is also a secret society of Immortals called the “Eternal Cage,” with its own rules and ambitions.
