Danganronpa 0: Birth of Despair

Back when Hope's Peak Academy first started recruiting young and talented people from around the world in order to research their talents, there was a different tragedy that had struck a group of students way before Junko Enoshima spread her despair to the entire world. The officials at the school all had kept this tragedy a secret as an attempt to avoid spreading any influence of despair to any other students, staff, or just people around the globe. After Makoto Naegi defeated Junko and restored Hope's Peak Academy, he discovered diaries that had documented the events that had happened prior. The events of the tragedy. Also known as, the first ever killing game.