A girl known only as "Mu" (無, meaning "Nothing") is shunned by her clan and forced to wear a black mask as a cursed shrine maiden. After suffering cruel treatment at the hands of her stepmother and stepsister, she seeks solace by a lake at night. As she practices her dance alone, a young man in a military uniform appears before her. Mu is startled to see that he bears the same curse mark on his tongue as she does, but after watching her dance, he simply hands her a folding fan and leaves. The next day, an officer from the imperial capital and a first-class exorcist named Tokiwa Kazuki arrives in her village—and it turns out he is the very man Mu met the night before!.