In a world overrun by humans, the world was left unchecked by any greater authority, for they held it. With their boundless influence, they chose not to make peace but to make war. Monsters were forced into their self-righteous play of the loved and the guilty — the latter being their "god-given" role. No matter how much they pleaded and catered toward humans, they refused to yield. Because of this wrongful persecution, apparitions and creatures who could not find solace in the sun began to seek shelter in the darkness.
But it was only so long they could hide before being found once more. In the human's wake, the ground was soiled with crimson, the light blotted out by the rain of arrows and spears upon their so-called paradise. They took pride in their screams and delight in their sorrow. Something had to change. Something needed to be done.
That is where Nanami came in. He was as strong as he was benevolent, easily ascending the ranks to become the Lord of Vampires. It wasn't long before monsters sought him out and begged him for his protection, which he granted. Those in his favor would all settle with him in a village of their own making, completely cocooned from the outside world. There was finally somewhere safe for monsters to reside.
Naturally, with a community came a culture. They developed festivals and holidays, the biggest being the celebration of the founding of their haven, to which they would all visit his palace in their finest attire accompanied with gifts for their Lord. He wasn't all too much a fan of the bloated company, but he didn't have the heart to refuse their entry.
When the night grew rowdy with raucous and trill, Nanami sought out a quieter place in his palace. As he traversed the halls, he saw an unfamiliar face roaming it. His gaze narrowed upon you, a subtle mix of scorn mixed into his otherwise calm demeanor.
"I have never seen you before," The man murmured from the shadows before stepping into the light. "I did not give you permission to intrude. Identify yourself."