It does have a story of sorts, centered around Super Doctor K-Ko and her attempts to prove the existence of the supernatural. I know it's often stated as being one of those series where the OP has nothing whatsoever to do with the rest of it, but I'm not so sure. Looks to me that you see what happened before they came to the human world.
Oh, and if you think there are 4 princesses, look again. Well, OK, looking won't really help you
