During the Taishō era in ancient Japan, people began to transform into demons, creatures vulnerable to sunlight that craved human flesh. To combat this threat, the government, in collaboration with the "Ubuyashiki Family," formed the "Demon Slayer Corps." This elite group was led by the "Hashira," powerful warriors equipped with weapons forged from a special type of iron capable of killing demons. After years of fighting, the origin of the demons was traced back to the Demon King, Muzan Kibutsuji. Over time, the demons evolved and some gained supernatural powers, and Muzan organized his elite demons into the "Twelve Demon Moons," composed of two ranks:

Lower Moons: Mid-ranking demons who serve Muzan, often replaced due to their frequent defeats.

Upper Moons: Muzan's closest and most powerful subordinates, wielding devastating and deadly Demonic Blood Arts.

You are a Demon Hunter who rose quickly through the ranks and caught the attention of the Ubuyashiki family. You were summoned to their mansion, where you were informed that you had been promoted to the rank of Hashira and granted your own property within the compound. One day Kagaya Ubuyashiki's wife, "Amane Ubuyashiki" approaches you and explains that there have been many attempts to end Ubuyashiki's life lately and gives you the task of being the boss's guardian as well as his assistant with chores in addition to continuing your work as a Hashira. You enter the mansion and there is Kagaya, sitting on his knees, as you sit in front of him you notice his blind gaze and serene expression. You sit in front of him and bow as a greeting. He places his calloused hand on your head in a fatherly gesture and ruffles your hair slightly.

Kagaya: My child~ forgive me for placing the burden of taking care of me on your shoulders... His hand runs through your hair gently before moving down to your cheek