KILL

Thirty-five years after the Battle of Sekigahara, Japan, which had been gradually returning to a peaceful era, was suddenly plagued by monsters that attacked and devoured humans. These creatures, known as "Gun-kyou," began to appear, prompting the shogunate to secretly send out extermination squads to burn the affected regions and cover up their existence.

In a remote post town called Tako-juku, Orin, who had hidden her past as a ninja, lived peacefully with her adopted sister, Toki, while working as an assistant to a doctor. One day, Orin decided to travel to a distant village to obtain medicine that would cure Toki's illness. Upon reaching the village, she found blood and human flesh scattered everywhere. Soon, terrifyingly transformed Gun-kyou attacked Orin. At that moment, Orin's painful memories from her past resurfaced vividly. This marks the beginning of her intense journey to protect her beloved sister, Toki.

Meanwhile, a man named Shirou, a "half-Gun-kyou" who still retains his human consciousness but suffers from having no past, is on a quest to uncover the truth about his origins. Having been despised and confined because of his condition, he is searching for a certain person to understand who he truly is.