Umezu-san's characters react to their extreme situation in realistic ways: some freak out, some keep a cool head, some commit suicide, some act selflessly. And many are willing to follow the lead of a strong (or brutal) personality. The body count starts rising quickly and the sixth graders have to begin taking on leadership roles and dealing with some dangerous grown-ups in their midst. Some discoveries are made about what seems to have happened and exactly how dire their situation is.
And back home, our hero's mother is, understandably, losing her mind. Or is she?
Drifting Classroom vol. 2 and vol. 3 are both available from Right Stuf, Intl., an online retailer specializing in anime and manga.