Mamotte Shugogetten!

まもって守護月天

Tasuke Shichiri is the envy of his friends because since his parents are always traveling he can do as he pleases. It's a surprise present from his father that keeps him from being lonely: an odd ring known as the shitenrin. From it comes a moon goddess named Shaorin, dedicated to protecting her "master" -- no matter how much of a mess she makes doing it!