I mean, the plot of the Dresden Files really does feel like a good anime plot, and if the Japanese had thought of the plot first/bought the rights to a Japanese adaptation of the Dresden Files, what might have come out of their efforts?
I can already think of a synopsis.
26-year-old Kabuto Kawanari (played by Matsuyama Kenichi of Death Note fame) is a highly-intelligent private investigator who aims to bring true order to Tokyo. There's a twist, though. He is also secretly a highly-powerful wizard prodigy who solves the supernatural cases the Japanese police are not equipped to solve. However, as he solves more cases, three things become clear. One, Tokyo holds a dark secret that was kept well-hidden from the public for millennia. Two, every case he has solved might be connected in one big super-case. Three, he's probably going to have to deal with his past sooner or later...