What had happened:

Five years ago the first Mitomi was over come by an ultimate darkness. Many died, hundreds probably. Many of those escaped and are just now flocking back to join the newly opened school, hoping to see old friends. Praying they are alive.

Those who are just coming for the first time aren't told of past happenings. Why? Well because the old principal YayoToshi managed to capture the darkness and keep it dormant inside his body. But YayoToshi disappeared. Never to be seen again.

Why is this a problem? Well YayoToshi was about fifty when this all happened five years ago. And while he was spry in his age, after battling darkness and encasing it inside him...well that takes a lot out of a person. So what happens to that darkness when YayoToshi dies? Obviously the darkness wanted something out of the school. But what was it? Will it return?