Angel’s Egg is an atmospheric, abstract, and symbolic film, so viewer interpretations will abound. Director Mamoru Oshii, though, explained exactly what it’s about:
Oshii said in a 1985 interview with Animage that the contents of the egg are supposed to represent dreams and hopes, something that may or may not exist, and that while the girl believed in what was in it, by breaking the egg, the boy showed that what she believed in did not exist. Regarding the bird the boy talks about, though the girl shows the boy an angel fossil in order to convince him that the bird does exist, Oshii has stated that the angel is not the bird. Oshii also said that the ending was one with salvation for the girl, but he did not want it to be shown in a straightforward way, and made it hard to understand.
His explanation leaves some room to interpret details, and if you pay attention you can pick up the clues. With what I saw, Angel’s Egg is also simply a journey into adulthood, and in specifically the girl’s case, it’s a forcible rejection of the childish and ascent into adulthood.
Oshii doesn’t equate but links the egg with the girl herself, with this shot. Notice the shapes. She’ll need to break out of her shell to evolve into an adult:
In a world with a desaturated color palette, color is going to play an important part when you see it.
The red, phallic tank-like vehicles that introduce the boy to the girl are pointing right at her. She is about to enter the world of men:
The red and pink of the girl’s dress and cloak imply the impeding menarche, and other red things she interacts with reinforce that idea. She dumps out the pinkish fluid from one of the bottles, rejecting adulthood for now:
After the bell tolls—her childhood’s end has arrived—she scavenges a bottle of red jam and starts eating it, now seemingly accepting her menarche and the first steps into adulthood:
Additionally, the pregnancy imagery when the girl hides the egg is very hard to ignore:
The climax occurs when the boy, a Christ-figure who represents time, destroys the egg, forcing her into adulthood. She chases after the boy and falls into a watery hole or crevasse of sorts, and meets her adult self as she enters into maturity:
The adult girl—er, woman—gives birth to real eggs, completing her “birth” into adulthood:
The shots of multiple eggs with the nascent birds/angels, atop the branch-like pedestals, strongly imply she gave birth to genuine life:
Not sure what the mechanical sun-eye at the beginning and end, the men trying to spear the shadow fish, or the Noah’s ark imagery represent, but there’s probably immaturity, growth, and adulthood parallels you could draw with those.
You can watch Angel’s Egg here.