Twin Princess of Wonder Planet

FushigiBoshi no FutagoHime (ふしぎ星の☆ふたご姫) is an anime and manga series. It was animated into a television series by J.C.Staff and TV Tokyo. The episodes ran from April 2, 2005, and ended on March 25th, 2006 with 51 episodes aired.

Plot
In the hollow Mysterious Planet, seven kingdoms co-exist, all of them lit by the Sun's Blessing from the Kingdom of the Sun, in the middle of the planet. The light of the core sun is necessary for the continued existence of all the kingdoms. Yet, something is causing the Sun's Blessing to weaken. If something isn't done, it will be the end of life in the Mysterious Planet. Fortunately, the twin princesses of the Sun Kingdom, Fine and Rein, have been endowed with the magic of the Prominence, and are looking for a way to fix things.