Hana Goyomi

When he was a child, the protagonist used to play with someone at the flower garden of his grandfather until the day his family moved to the city. Many years later, main character went to visit his grandfather, who felt ill at the hospital. He asks him to take care and rebuild his flower garden, because he can't do it anymore. When the protagonist went to visit the flower garden after a long time, he is stunned to see a desolated garden. And he becomes even more surprised to see that in this strange place live some flower fairies, who need that garden beautiful again in order to return to being healthy... [Translated from Getchu.com]