Totsukuni no Shoujo

From Seven Seas:
In a land far away, there were two kingdoms: the Outside, where twisted beasts roamed that could curse with a touch, and the Inside, where humans lived in safety and peace. The girl and the beast should never have met, but when they do, a quiet fairytale begins. This is a story of two people, one human, one inhuman, who linger in the hazy twilight that separates night from day.

Official Japanese:
Comico, Magcomi, Mechacomic, Piccoma