The story takes place in a world where there is a group of "immortals". Eternal life is not a blessing, but a supernatural phenomenon or genetic mutation called "Eternal Shackles." Immortals cannot die in conventional ways, but each "death" is not without cost: they may permanently lose part of their core memories, or strengthen certain emotions or personality traits, gradually distorting their identities. There is a mysterious organization "The Asylum" in the world, which may be dedicated to researching, managing and even trying to "cure" the immortals. At the same time, there is also a secret society "Eternal Cage" composed of immortals. They have their own rules and pursuits.
