Creator Breakdown: The original short story was written by Akiyuki Nosaka as a way to come to grips with his guilt over the real-life death of his younger sister, who he had been caring for after their parents died:
My sister's death is an exact match with the novel. It was one week after the end of the war. At the countryside of Fukui prefecture where I was, it was the day the restrictions on lighting were removed. It must have been the 22nd. It was evening, and I was picking up my sister's bones. I was coming home in a daze when I saw the village lit up. There was nothing like my surprise then. My sister died in my side of the world, and the light was coming back in the other.
Defictionalization: Of a sort. Sakuma fruit drops have been around since 1908, but every once in a while they're released in a commemorative tin that looks just like the one from the film.
Enforced Method Acting: In Japan, Setsuko's voice actress really was four years old, and her lines had to be recorded before her scenes were animated. Because the animators were not used to having to do this, they tried to avoid angles from where her mouth could be seen.
Jossed: A popular interpretation of the film is that it isn't an anti-war movie. Instead, it is aimed squarely at juvenile delinquents in 1980s Japan, with the message being, "When they were your age, your parents went through hell on earth, and this is how you choose to reward them?" In reality, this interpretation has more or less been jossed in an interview which delved into Isao Takahata's actual message and various opinions. The story is about people losing their ability to sympathize under trying conditions. The director does not consider Grave an anti-war movie because he fears statesmen could just as easily twist it into propaganda for a war to prevent such tragedies, and showing human suffering by itself cannot dissuade specific behaviors.