In this fictional world set in early 20th century Taishō-era Japan, man-eating demons roam the land each night and can turn humans into demons by giving their blood to humans. An organization unrecognized by the government kills demons to protect people, known as the demon slayer corps. Demons burn away in sunlight, and can only eat humans. They have increased strength, speed, regeneration, etc. A large scale war against demons is coming, so train low rank demon slayers to assisting in the war.