Garo

Garo focuses on the life of Kouga Saezima, who has assumed the title of Makai Knight to protect humanity against dark demonic manifestations called "Horrors". In his quest to purge them, he encounters a young girl named Kaoru whom he saves from a Horror, but learns that she is stained with its demonic blood. As a rule, those that have been stained by the blood of a Horror shall be cut down, or else they will die painfully in approximately 100 days. (wikipedia)