Based on the book of the same name by Ōshiro Tatsuhiro, this documentary anime chronicles the tragic wreck of the freight boat Tsushima Maru. The vessel was carrying a class of schoolchildren back to their homes in July 1944 when it was attacked and sunk by an American submarine. The film was produced by surviving family members of the Tsushima Maru. It combines a highly realistic and meticulously crafted depiction of the event with strikingly deformed character designs by Kiyomizu Kazutoshi.