Tengujin is a story about two twin brothers who live in a world where Eastern and Western Japan and splitting apart and have formed two warring countries. In this "idiot adult's world", many social issues press on society and drove it to war. Gods of the world, mainly tengu, influence the start and end of the events that lead to war such as Japan splitting into two, so the younger twin, Mozuku, desires to end the idiotic war the adults started and meets with the God of the West (Sai) with his older brother, Shinonome.
Zanouka, the second story in Tengujin, is about the former incarnations of Mozuku and Shinonome. Mozuku is a young bard who is the inheriting son of a feudal lord of a dead mountain with only poor people remaining on it. He keeps a rigid, realistic perspective on life and refuses to believe in things like tengu. While cleaning the tengu's small shrine, his beautiful voice attracts the attention of the tengu of the mountain, Tondonbou (Shinonome's former incarnation), who hides half of his face behind a mask. After meeting the tengu, Mozuku sets to seeking him out again, wanting to see what was hidden behind that mask.
(Source: Aku Tenshi)
Note: Series is on hiatus.