A detective broke down to his last yen picks up a sentient grimoire, and suddenly he's piloting a magic mecha to fight Lovecraft-adjacent horror in a city that doesn't care which one of them is actually in control. The show treats this premise like it's completely normal. The romance between Kuro and Al works because they're both trying to survive something bigger than either of them, and the ecchi moments land as nervous energy rather than distraction, which is harder than it sounds.

Kuro Daijuuji is a poor private detective in Arkham City. When the young head of the Hado Financial Group, Ruri Hado, asks him to find a magic book, he turns her down at first, but a large reward changes his mind. His search goes nowhere until he meets Al, a girl chased by the Black Lodge who turns out to be a powerful grimoire herself. The two form a contract that grants Kuro strong magic. Al then activates Demonbane, a deus machina belonging to the Hado Financial Group, to battle the Black Lodge's mechanical menace, and open war breaks out between the two sides. The series is a mecha action story with romance and ecchi elements.