Mana Sorcerer

Mana, the spirit of green living things, can be used for both good and evil, and an investigative office exists to keep the destructive power of Mana in check. Ruwen is a Mana Investigator who's been sent to a small town to check out a possible abuse of Mana situation. Once there, he meets the cheerful little girl Miniru, who eagerly guides him around the town. Could Miniru, who is suffering from a strange illness, have something to do with the Mana situation?
(Source: MangaHelpers)