Read manga: Mana Sorcerer

manga
Summary:

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? (taken from MH)