Kishin Houkou Demonbane (TV)

Kuro Daijuuji, a private detective in Arkham City, is hired by Ruri Hado from Hado Financial Group to find a rare magic book. The job initially pays poorly, but Ruri's offer of a large sum of money changes Kuro's mind. While searching for the book, he meets Al, a girl who turns out to be a powerful magical artifact known as a grimoire. The two form a contract, granting Kuro access to Al's magical abilities and unleashing the powerful mecha Demonbane in the process.