Kobato.

Synopsis

From Yen Press:
Meet Kobato Hanato, a sweet and rather simple young girl on a quest to have her single, dearest wish granted. But first, she must learn the ways of the world from Ioryogi-san, a gruff blue dog whose bark is just as bad as his bite! Under his “tutelage” (read: constant verbal abuse), Kobato puts her efforts into passing various trials of common sense so that she may obtain the key to getting her wish—a magic bottle which must be filled with the suffering of wounded hearts that Kobato herself has healed. But with Kobato’s common sense sorely lacking, she keeps flunking Ioryogi-san’s trials left and right! It looks like the road that lies ahead of Kobato will be a long one indeed!

Synopsis & details from MangaUpdates