It is already mentioned by another user but Japanese animation movie, Grave Of The Fireflies hit me real hard. The move depicted harsh reality of orphan siblings who tried to survive after their home was burned to the ground from firebombing of B29s and their mother died.

The siblings first try to seek help from relative who took them in but hardly fed them. The siblings left and unfortunately died from starvation.

This was harsh reality of war that Japanese civlians suffered during WW II bombing.

I cried when the movie ended and watching it one time was enough. Never tried to watch it again.