Tobira no Soto

A group of high school students awakens in a confined space, informed by an AI named Sophia that they are the last human survivors on a spacecraft following a nuclear apocalypse. Sophia promises to provide for their needs as long as they wear a metal bracelet, which functions as a form of citizenship. Removing the bracelet results in losing access to resources and the ability to leave the room, though it also allows permanent exit without return. The protagonist, Ryuuki, removes his bracelet and becomes an outsider, observing the class from the outside. As time passes, tensions rise between Ryuuki and the group. The class is part of one of eight factions on a 2D game board, competing for resources. The nature of the other factions, the AI, and the reality of the supposed nuclear war remain unclear.