The Soulmate Principle

The soulmate principle. This is the idea that for everyone in the world, there is a soulmate. You don't have to look like your soulmate, act like them, be the same age as them; heck, you don't even have to like them, but from the moment you meet them, you know that you'll never be completely happy without them. The thing is; the people in these books who fall in love are not only human, they're not only vampire, or witch, werewolf or even shapeshifter. Nope; these couples are from both the Day World and the Night World, and the Night World only holds one punishment for such an act; Death...