Grave of the Fireflies [Hotaru no haka]

"During World War II a brother and sister face the cruelest enemy of all, indifference. Inevitability does not dampen their resolve, but makes it more tragic when resolve finally gives way. Fireflies always expire quickly when trapped, their light is always so inspiring to gaze upon no matter how short lived. Watch the fireflies dance in a world where silk doesn't buy five pounds of rice, watch the fireflies descend into the cracks of society and be forgotten." Source: http://www.anime-planet.com/anirec/143.html