"Grave of the Fireflies" is not so much about war as about society and how people will look the other way and allow other people to suffer. The idea of
war is simply an extension of this idea- we can kill people and feel no qualms, so long as they are far away and never exposed to it. There is a lot of evidence for this- from the opening scene, where the main character is dying in the
train station- nobody tries to help him, they simply react in
fear at being exposed to his circumstances, then they continue walking as if nothing had happened. Also throughout the movie we are given glimpses of other, luckier, peoples lives and we see that they have not lost anything.
I think that Starrynight's comment about Takahata having lost something in his childhood is undoubtedly correct, the feeling that one gets in the opening of the movie is one of loss, as we see the children riding on the now-nonexistent subway through the now-destroyed city.
The main character, Seita, seems almost constantly baffled as to how circumstances could so much for the worse.
He is very optimistic, always putting a good face on circumstances and never asking for help from others if he can avoid it. He keeps the fact of his mother's death from his sister for as long as possible.
Seita's aunt is probably the "worst" character in the entire movie, as she and her family eat a great portion of Seita and Setsuko's leftover food and then lets them leave her home. Again, this is because Seita told her that he didn't need her help- and she looks the other way and allows him to leave. Yet at the same time she is the most practical person in the movie. Whereas Seita dies mainly because of his pride and refusal to apologize to his aunt- he takes up robbery rather than returning to her home.
Although many say that this movie can be appreciated by anyone, I think that it would obviously have special significance to Japanese people, particularly to those raised in the post-WWII years simply because such a story is something they or somebody close to them has lived.
Naturally, there is a recurring firefly motif in the film- IMO the fireflies represent life, which is both beautiful and fragile at the same time.
I wish that more analysis would be done on this movie as I personally do not know enough about the subject to do a thorough explanation of the themes in the movie- at present all I hear is "that movie was really sad and also really good", but nobody seems to be able to figure out why...I don't know that the director was necessary trying to play this movie to make a sob story, as I think that if anything the movie was understated in being sad, a fact which begs the question "Was the director of this movie trying to make a "sad" film?" This movie is known for being a sad story, but I for one did not cry at any time during watching it. Instead I think that it could be thought of as a comment on life and its transient nature.
Also as a final note, the cave where the kids lived in the movie is located in Nishinomiya, Japan- one of my classmates has to walk by it every day on his way home from school. Creepy, huh?