Kaijuu no Kodomo, Puparia Recommendations
First of all - they both share a similar artstyle, which is very unique to both.
Second, both share a very similar atmosphere and has the theme of fanatsy in a world that is pretty much similar ot ours, with a lot of moments that just feel magical. If you liked one, you should definetly watch the other (though I think the Manga of Kiajuu no Kodomo is better, but the adaptation is also amazing).
Both are anime with majestic synesthesia, that hold the viewer in a magical way, using visual art to compose an indescribable breathtaking feeling.