Sunzuku no Teiou Ori wa Dokuyaku

In the underworld of Toukai, a realm of eternal darkness, the aristocratic families vie for power and dominance. Kunou, a young and powerful demon lord, seeks to ascend to the throne, but his ambitions are hindered by the tyrannical rule of the current ruler, Yousuke. As Kunou navigates the treacherous landscape of Toukai's politics, he discovers a mysterious, ancient artifact known as the Sunzuku no Teiou Ori, a legendary sword that holds the key to unlocking unimaginable power. With the sword in hand, Kunou must confront the darkness within himself and the gods themselves in order to claim his rightful place among the ruling elite and bring about a new era of prosperity to the underworld.