Demonbane is a tV series anime that premiered in spring 2006.

About the production: the story comes from a visual novel, there are 12 episodes of about 25 minutes and its current status is "finished".

Its main genres are action, ecchi, mecha and romance, with themes such as Henshin, Female Harem, Magic and Ojou-sama.

On AniList, Demonbane has an average score of 60%, an average score, and appears on 6,377 users' lists.

Kuro Daijuuji is a poor detective living in Arkham City. One day, he was requested by Ruri Hado of Hado Financial Group, to search for a magic book. While he initially refused, Ruri offered him a large sum of money upon completion of her request, in which bribed Kuro to accept. As Kuro searches for the book, he unexpectedly runs into Al, a pretty girl that is actually a powerful grimoire. They forge a contract with each other, bestowing Kuro with powerful magic. Soon afterwards, Al also activates Demonbane, a deus machina owned by the Hado Financial Group, to combat the mechanical menace from the Black Lodge. With this, the war between the Hado Financial Group and the Black Lodge begins.... (Source: Anime News Network)

Official synopsis from AniList.