Special high school students throughout Japan are transferred to Kibougamine Academy because they excel above all other students in a certain way. The protagonist, Naegi Makoto (excels in Luck) arrives on the first day of class only to fall unconscious after he steps through the gates. When he wakes up, he meets up with 14 other students who went through the same experience, and they find that all possible exits have been sealed shut.
The 15 are then informed by Monokuma, a black and white robot bear who appears to be behind the whole affair, that they are playing a game and the only way for them to leave the school is to "graduate". To do so, they must kill another student and get away with it. A trial will be held after a corpse is found, and if the culprit is found guilty, they will be executed and the game will continue. If they are found innocent, they will graduate and be able to leave, while the rest of the cast gets executed in their place...