Dark Clan

The Dark Clan (闇の一族 Yami no Ichizoku) is the clan of the demons. They are the mortal enemies of the Light Clan.

Although they are often dubbed the clan of the demons, the Dark Clan members are not only demons. They are anything that somehow interferes with the natural order.

History
The Light Clan and the Dark Clan had a war, fighting for centuries long. In the end, the Dark Clan lost the war and all their powers and luck were sealed away. This is the reason why they look like ordinary humans. They were cursed with a 40,000 yen per month (around 370 USD) curse.

One day, Yuko Yoshida, descendant of the Dark Clan, wakes up with horns and a tail, having caused a lapse in the seal.