 If you liked
Spiral: Suiri no Kizuna
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 ...then you might like
Fantastic Children
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Even though these two series are quite different in many ways, they both deal with a group of special/different children whose past and future look kinda gloomy and the present is full of mystery. Both anime raise a lot of questions at the beginning which will keep you watching till the end.
(The ending of Fantastic Children is much more satisfying though - in terms of answering the questions it raises.)
And they are both fun to watch.