Killers always tried to do things soundlessly. Even during the time when the stone castle was full of killers, they had to hide themselves in the dark for most of the time. Besides the training ground in the eastern part of the castle, killers were rarely seen anywhere else.
But after those killers had left, the people living in the stone castle could distinctly feel the emptiness. These tall stone walls, which used to seem very mysterious due to the existence of killers, were now merely stacks of stone bricks. Walking in those quiet alleys, people no longer had to worry that someone dressed in black with a narrow saber would abruptly show up. Instead, they were afraid of the vengeful spirits of the numerous victims that had been slain over so many years.
Killers killed people, so they were the only ones who were able to keep those spirits in the stone castle under control.