Enter a different kind of L.A., where mobsters are daemons, high school students are possessed, and frozen yogurt is the first step to solving every problem.
Kai is possessed by his demon, Akuma, and has been for eleven years. And for eleven years he's managed to keep that tidbit of information a secret. His parents think the strange side effects of having a pet demon are due to a physical disability, but boy and demon have reached a happy equilibrium, and leaving Kai's parents in the dark is essential to that.
Life is, well, not grand but serviceable until a mobster recognizes Kai and Akuma for what they are, and he needs Kai's power to break out a very dangerous criminal. As Kai gets sucked into the L.A. supernatural underground, he finds that the mob knows more about his demon than he does and what he doesn't know is very, very dangerous.
As Kai and Akuma try and navigate through the sea of other monsters in the dark, they have to do it while pretending to be the most mysterious creature of all: a normal teenager.
Some songs inspire the characters, and some characters inspire songs (not any of these characters, but, well, you get the point.) Spoiler Alert though, if you haven't finished the book, you might want to wait.