Minami—along with 15 others—wake up in a somewhat foreign location. All remember one main thing. They thought they had died. Tokumei, the leader of this place informs them all that they are in a killing game, where they have only one year to end with one survivor. Each character has a special power called a Seigyu which lets them control any one concept, ranging from frequency to recoil. Once someone is killed, the killer has a chance to gain some very important, unknown information unless they are caught. A meeting is held where everyone—although they are not required to show up—attempts to find the culprit. If they successfully do so, the culprit is punished.
The story often swaps between perspectives, often deceptively so. The story explores the characters actions, emotions and interactions in this wild game. Minami starts with a handicap, and she has to deal with being behind, but there must be some deeper reason she specifically has a handicap, right?
KSSJ Wiki for good version