As part of a special test, the school has brought the students to an uninhabited tropical island where they must now live for a week. Their performance on the test can have an enormous impact on the point standings of the four classes.

With the panty thief incident already eroding Class D's trust, Horikita finds her leader key card stolen. While they try to figure out who did it, the base camp is thrown into chaos with a new incident of arson.