Reina Kisaragi, a news reporter, deliberately gets herself thrown into prison after receiving a tip that Haruna, her missing sister, may be inside. But once imprisoned, she discovers that the inmates are forced to participate in a twisted game, created as a betting ground for the rich and elite. Politicians and CEOs alike gather to watch, as the female prisoners are forced to fight each other to the death. The rule: 15 kills, and release from prison is guaranteed. The women battle desperately to try to earn their freedom, but in order to save her sister, Reina must discover what she is truly capable of.