Corseltel No Ryuujutsushi summary:

Corseltel, a sacred land where dragons and beastmen reside. Protected from the outside world by valleys and mountains, its inhabitants, including dragon mages (ryuujitsushi), live in harmony. The dragon mages are able to borrow and use the dragons' magic, but have to care for and look after the dragons in exchange.Several years ago, the late wind dragon mage picked up a child floating down stream in a crate. Now, the child has grown into Corseltel's greatest dragon mage, able to use all seven types of dragon magic: fire, earth, wood, water, wind, light, and dark. More like a dragon babysitter, caring after seven baby dragons, these are the adventures they face.