Help

Hey guys! I wonder if you guys can help me finding a manga. I read it long time ago and I don't remenber what was it's name. The only things I remenber are: it was about a child that goes to a cursed island where a demon lives, but although he isn't evil, he keeps frightening the child, because when the child stops fearing he, he becomens invisible. Or something like this. At some point, the demon gives the child a blue flower. At the end, the child can no longer see the demon, and the demon makes the island spark in a blue color. I know my explanation is a little confusing, but if anyone knows which manga is this please help me! (〜￣△￣)〜