Ember, left, voiced by Leah Lewis, and Wade, voiced by Mamoudou Athie, have a fire-and-water love story in “Elemental.” (Disney/Pixar/The Minnesota Star Tribune)

"Elemental" is the most emotional Pixar movie since "Inside Out," and the hardest to make sense of.

It's a full-on romance, set in a world where characters belong to one of four groups that pretty much stick to themselves: fire, water, earth and air. Main characters Ember (fire) and Wade (water) fall in love — "When I met you, I thought I was drowning, but that light inside you has made me so alive," is how Wade puts it. Voice actors Leah Lewis and Mamoudou Athie, respectively, bring huge depths of feeling to their performances as a couple whose communities — especially Ember's traditional parents — don't approve.

Pixar has sometimes been shy about love stories, but that's the part of "Elemental" that works best. That has a lot to do with director Peter Sohn's willingness to commit to the central romance, which has humor but gets into pretty dark emotional territory for both of its unmoored main characters, whose parents are not wrong when they point out the tremendous differences between them.

It also has to do with the clever character design. In the time-honored cartoon tradition of Squidward, Winnie-the-Pooh and Donald Duck, Wade wears a shirt but no pants. But, otherwise, these are very untraditional characters. It could seem like a drawback that both Ember and Wade are visually amorphous — the flames that constitute her body and the water that makes up his are in constant motion — but they're always clearly these two vivid, passionate characters.

What works less well in "Elemental" is the fuzzy central idea. The four-elements thing wants to be a metaphor for immigration, with some of the elements feeling less-than and unwelcomed by some of the others. We're certainly accustomed to storytelling that presents cross-cultural lovers from different worlds — Romeo and Juliet, Tony and Maria, Ariel and Prince Eric from the current "Little Mermaid."

But, unlike in the well-defined concept of "Inside Out" or the slightly less clear one in "Soul," the "Elemental" territories are so amorphous that we aren't sure what their rules are, especially since Ember and Wade genuinely do seem to have an issue that makes it impossible for them to be together: A well-tossed bucket of him will put her out forever and it wouldn't take much of her to make him evaporate.

Just a couple of minor but confusing dilemmas: A running joke is that the water people cry all the time, but so does Ember. What's that about? And earth and air are clearly important elements, but both are virtually ignored in "Elemental." All of this makes you feel like the movie might work better with human characters, who wouldn't always be at one or two allegorical removes from the story that's being told.

The murkiness is not a deal-breaker by any means. I was moved by Ember and Wade's romance and "Elemental" has flashes of insight into the complicated bonds between immigrant parents and first-generation children.

But I have to admit my mind kept going back to "Carl's Date," the brief "Up" sequel that plays before "Elemental" and that stands out for its simplicity and warmth. Is it wrong of me to wish I were watching a full-length version of that, instead?

'Elemental'

*** out of 4 stars