Twin Princess of Wonder Planet

Fushigiboshi no Futagohime (ふしぎ星の☆ふたご姫, lit. "Twin Princesses of the Wonder Planet") is a 2005 Japanese animated television show directed by Shōgo Kawamoto and with Jun'ichi Satō as chief director and character designs by Birthday. Following Birthday's original concept in 2003, it was taken by Nihon Ad Systems and TV Tokyo and was reproduced into a full-length series in 2005. A sequel titled Fushigiboshi no Futagohime Gyu! premiered in 2006 and aired until 2007.

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.

Official

 * http://futagohime.jp/fushigi/menu.html
 * http://www.tv-tokyo.co.jp/anime/futagohime/
 * http://futagohime.jp/