This System Doesn't Want Me Alive.

Is it a life or death situation? Is it hope or despair? When five people received a mysterious invitation letter at the same time, a life-and-death situation about them immediately unfolded, as if invisible hands were controlling the situation. Horrible nursery rhymes... Corpses resurrected from the dead... Horrifying experiments conducted more than 20 years ago... Can they break through the many tests and uncover the people and the truth hidden under the abyss?