Nurarihyon no Mago: Sennen Makyou

ぬらりひょんの孫 千年魔京

Long before Rikuo Nura was born, the legendary youkai Nurarihyon, leader of a "Night Parade of One Hundred Demons," fell in love with a human woman. Though the two would initially find happiness, a threat from the terrifying fox-demon Hagoromo Gitsune would get in the way of their relationship.

In the present, Rikuo has taken his rightful place as the heir to the Nura Clan. While he has accepted his youkai side, he must continue to maintain the secret of youkai, a difficult task when faced with the Keikain onmyouji clan and his youkai-obsessed friend, Kiyotsugu. Even so, Rikuo will do what he must to protect those important to him.

The reappearance of the sinister Hagoromo Gitsune marks the start of Rikuo's most fearsome trial yet. The frightening creature bears a personal vendetta against his family and will stop at nothing to see her dream come to fruition. The world stands at a precipice, an all-out war that will drag Rikuo centerstage.

(Source: MAL Rewrite)