No matter how peaceful things may appear, some things weren't meant to live in our world. The twelve ghosts who lived together deep in the forest weren't an exception to this fact. Bad things would happen if they stayed for too long, they knew that very well. So they came up with a plan.

Help each other move on.

But then again, does the idea of a ghost helping another ghost move on even make sense? Surely, a lot of sacrifices had been made in the process, and probably a lot of bad decisions as well.