The 1st chapter is quite obscene - It throws you right to the sex scene between a vampire and a demon - but they didn't know that about each other. The demon drank the vampire's 500 years old blood thus making a contract between them - The vampire can feed only on the devil now. So they start a sex relationship. They end up together forever.
+ during the story there was a murder case. The culprit was a human who fell in love with another human and a police officer. He killed people by beating them and making bite marks on their necks to bleed them so it would look like a death by a vampire. So the police officer arrested the vampire form the first couple - making the demon quite pissed and the demon killed the police officer. The criminal lost his desires to kill anymore (he wanted to be precious to the police officer - he's kinda messed up).
Extra chapters are about that murdere/criminal and another demon, who's trying to convince the human to kill another people, so he could eat the human lives (aka stones), the murdere took/killed.
In the end (extra 3) the demons from both stories take possessions of the other partie's (other dudes in the relationship) souls.
I'm Yours, Blood and Soul