Once upon a time, in a far, faraway place, there were two lands. The world was divided into an inner land and an outer land. People feared the outer land, inhabited by eerie beings, the carriers of curse. One day, on the border to the inner land inhabited by humans, one such being finds a girl on heaps of abandoned dead bodies. The girl says her name is Shiva and shows affection to the "being" who found her, calling him "Teacher." This is a story of two people—one human, one inhuman—who linger in the hazy twilight that separates night from day.

Touch not the Outsiders, lest ye become an Outsider. But when two creatures belonging to opposite kinds - a lost little girl from the Inside and a demonic beast-looking Outsider - initiate an impossible coexistence on the same side of the forest, their bond seems to transcend their incompatible natures and the unnamed curse that has divided the world.

Hazuki and Aoi are classmates but their relationship outside class is fraught, and outside school non-existent. But when both girls are drawn to helping an elderly woman, they're forced to interact, confronting their differences and similarities as well as their deepest secrets.