Even during summer vacation, lone wolf Horikita would rather remain locked in her room studying than interacting with others. One day, Ayanokouji invites her to visit the pool with some of the others.

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.

Survival test is coming to the end. Things don't look well for 1-D. Key card is stolen. And now Suzune is forced to withdraw due to her sickness. Kiyotaka will try to turn things around.