Life Tree's Guardian

Life Tree's Guardian summary:

The 15-year-old school girl May Thomsen lives an ordinary life, until one day a speaking wolf (called Wolf) appears, telling her, that he's the guardian of the Life Tree of his distant home. He's looking for the five splinters of the tree's heart that have by an accident vanished into May's world. Since May has always dreamed of an adventure she insists on helping Wolf and becomes a Life Tree's Guardian.