This animated film tells the story of a young Japanese girl's relationship with her grandfather, a postmaster and amateur geologist. When the neighboring Mount Usu erupts during World War II, he records its activity. As he witnesses the birth of a new mountain named Showa Shinzan, he transcends the misery and folly of war that surrounds them and teaches his granddaughter a valuable lesson about life. Evoking the tradition of Bunraku puppetry, this animated film is based on actual events.