From Aerandria Scans:
Long, long ago four witches of great power were sealed away in a mysterious kingdom ruled by a mysterious king. To this day, the legends say that the one who finds their graves will have their wish granted - however impossible that wish may be. Daidai, a girl who escaped from the king's treasury, believes in those legends and starts her journey through the magic kingdom, accompanied by Matsuba, a small boy-robot who loves her. What really is their destination? And what wish shall the graves of the four witches grant the unlikely companions?