Choujin Densetsu Urotsukidouji  

A Lenda do Demônio, Urotsukidoji, Urotsukidōji - La légende du démon (OAV), Urotsukidoji: Legend of the Overfiend, Urotsukidōji: Legenda o Superdemonie, Urotsukidōji: O Demónio de Overfiend, Urotsukidouji

It's said that there are other dominant civilizations besides humans on our planet. These include the Makai, a demon race, and the Juujinkai, who are half-human, half-beast creatures. Every 3,000 years, a powerful being known as the "Choujin" emerges to maintain balance among these three realms. In modern Japan, after searching for 300 years, Amano Jyaku from the Juujinkai has discovered that the Choujin resides within high school slacker Tatsuo Nagumo. Now, along with his sister Megumi and sidekick Kuroko, Amano must safeguard Nagumo and his new girlfriend Akemi Ito against the Makai, who believe that Nagumo is not the Choujin but an evil force threatening all life on Earth.