Fushigiboshi no Futago Hime

Deep in space lies the hollow Wonder Planet, where seven kingdoms co-exist, all of them lit by the Sun's Blessing from the Sunny Kingdom in the planet's center; this light is necessary for the continued existence of all the kingdoms. However, something is causing the Sun's Blessing to weaken, threatening to plunge the Wonder Planet into darkness. Fortunately, the twin princesses of the Sunny Kingdom, Fine and Rein, have been endowed with the magic of Prominence, and have been tasked with finding a solution to this problem, assisted by a fairy named Poomo. On the other hand, they also happen to be notorious as "the most unprincesslike princesses in Wonder Planet history," often slacking off on their studying and sporting highly carefree attitudes. Can they save their planet and all its kingdoms? And can they truly become worthy princesses?