Blood-C

Saya Kisaragi appears to live a gentle life in a quiet village, spending her days at school and helping at her father's shrine. At night, however, she takes up a sacred sword and hunts the Elder Bairns, monstrous creatures that prey on humans. Saya accepts the duty without hesitation because she believes protecting the village is a promise she must keep.

That certainty begins to fracture when the monsters speak of an old covenant she has never heard of and a strange dog questions the origin of her promise. Unexplained visions, inconsistencies in her memories, and increasingly brutal attacks force Saya to ask whether the peaceful life she protects has ever been real.