This film just changed my entire view of life. It made me feel human and cry like I had never done. After watching it, I just couldn't see a simple candy without crying. That's the potential of The Grave of the Fireflies, a powerfully sad feeling that I had inside my mind for at least three months. Animation can perfectly tell us about human's cruelty and humankind's reality, and this film demonstrates it in so many ways.
Hotaru no Haka is the anime film everyone should watch before dying. I always consider significant to find a metaphor inside a story, this film has it. You will see that fireflies are depicted as human's weak brightness looking for a better world, the poorly awakened souls of those who died in the war, the light of life, and also the small shine of a world based on utopia. The film knows how to join subtle with the crudest reality.
Hotaru no Haka is, probably, one of the most beautifully, brilliantly, and brutally depressing films ever made. You must watch it, but you also shouldn't. It's up to you.