Yomi no Tsugai

Yuru lives in an isolated mountain village believing that his twin sister Asa is kept apart from everyone because of a mysterious sacred duty. Everything he knows collapses when armed outsiders descend on the village, the girl he thought was Asa is found dead, and one of the attackers claims to be his real twin sister.

Rescued by the outsider Dera, Yuru is cornered into summoning a paired set of supernatural beings known as Tsugai. From that moment, he is pulled into a conflict far larger than his village. The truth about his birth, his sister, and the secret the adults around him worked so hard to hide begins to surface one dangerous piece at a time.