Sayounara Kaba-kun

A mixture of live action and animation telling the true story of the animals of Tokyo's Ueno Zoo during the harsh days of bombing raids and shortages that took their toll during World War II. Focusing on the hippos, who were eventually butchered for food in the closing days of the conflict, Newtype called the story, "a study of the tragedy of war and a prayer for peace."

(Source: The Anime Encyclopedia)