Everything I've been craving to read and more. 
 Kate Harker - daughter of the north, human, and striving to be just like her father and gain his respect. 
 August Flynn - son (??) of the south, sonai, and striving to find balance between good and evil. 
 "Corsai fed on flesh and bone, Malchai on blood, and whose it was meant nothing to them. But the Sunai could feed only on sinners. That's what set them apart." 
 The city is divided between north and south with a sea of monsters in the middle. Monsters that were created based on the worst acts of humanity. Anytime murder or some other violent crime is committed a monster is created in return for that sin.