Mushi-Shi S02 E13 Lingering Crimson

"The cure lies in the curse."

At dusk, about to go home after playing with her friends, a young girl named Akane found a shadow without a caster. On that same day, she disappeared. Several years later, Ginko is told the story of Mikage, a girl who appeared with no memories at Akane's village shortly after the vanishing of the latter.