As the lethal Medousa virus spreads worldwide, petrifying victims with no possibility of cure, humanity stands on the brink of annihilation. The sole hope lies in a startling proposal by Venus Gate Corporation: to place 160 individuals into cryogenic stasis for up to a century, or until a remedy is found. Kasumi Ishiki is among the lucky few chosen for this program. Although she dreads being separated from her twin sister, Shizuku, the sisters hold onto the hope of reuniting someday. Upon waking, however, Kasumi discovers a world far from her expectations. The cryogenic facility is overgrown with thorns, and bizarre monsters launch attacks against them. While the majority of those who awaken perish in the initial chaos, Kasumi and a handful of survivors start to explore the labyrinthine complex. They aim to uncover the mysteries of Medousa and the true motives behind Venus Gate Corporation.