A Lullaby Resounding in the Gray World

A girl who embodies "Death," calmly bestowing death upon humans as dictated by "Fate." One day, while chasing a white monster marked for extermination, "Death" inadvertently steps into a restricted area forbidden by "Fate."

At a lake deep within, she is dragged into the water's depths by her own reflection on the surface. What she encounters there is—