There's this anime that I can not, for the life of me, remember the name of, can anyone help?

Ok, so from what little I remember, there are children, I think 8-10 of them, most with blonde hair and blue eyes. No parents, they have intelligence superior to adults, but they need to keep finding somthing that helps them keep this knowledge or they turn into normal children and forget all of the knowledge they had. They had it hidden somewhere bellow ground.... I think..... One of the children (a boy) wanted to lose the knowledge and be normal and then does so, and the others leave him behind. The names of the children were European, I think one was French, and there was a Dutch one and a German one, but that's all I remember! So anyone have any clues?