학교로 낙하한 중형구체를 뒤로하고 성진고 학생들은 군사훈련을 받기 시작한다. 훈련이 익숙해지는 아이들, 드디어 첫 실탄사격날 첫 훈련 이후 처음으로 학교 밖으로 나가게 되는데... 그러나 학교 밖으로 나오지 말아야 했던 걸까?
After spheres from the sky drop to the ground, military training begins for the students to ensure their safety. However, the students find it too demanding and have a difficult time. As students head to the shooting range to learn how to shoot, they get caught off guard and fall into a crisis. Meanwhile, a student gets killed by one of the spheres.
