Haruka Nanase is a graduate student studying genetics. Having lost his younger stepsister Shiori during a catastrophic flood, he has been unable to accept her death even as time has passed. He continues to believe that she is alive. One day, his professor asks Haruka Nanase to analyze the DNA of 200 year old human skeletal remains excavated in India. While examining the human skeletal remains, he finds a 100% DNA match with his stepsister Shiori. He is baffled by this seemingly impossible test result. Meanwhile, people related to the case are murdered one after the other. The human skeletal remains kept in the laboratory are also stolen. Chasing this mystery, which is somehow related to Shiori's life, he steps into a vast darkness that connects the past and present.