Akira, Kaijuu no Kodomo Recommendations
Both series use a lot of allegories to explore themes like the birth of the universe, singularities and human nature. Also, both of them are a visual delight, using some psychedelic sequences at the final leg of the movie to illustrate their message.
Both are convoluted adaptations of a longer material. I think both movies are still very appreciable by their presentation; both have a certain mysticism to their setting and they capitalize on it to give it appeal.
For some reason, after watching Kaijuu no Kodomo, it reminded me of the ending of Akira. Both of the animes' ending were open for interpretation. Akira is focused on finding the mystery behind the entity Akira and Kaijuu no Kodomo is focused behind the mystery of Umi and Sora.