The Shadow Rot is a dark and immense epidemic released onto Kudao after the events of Yamamura. The effects include lung failure, crucial pain, and insanity. Vessels (someone infected by Shadow rot) can resist the hateful emotions and can stay somewhat sane to a degree, but those who embrace the hate can make the pain worse and worse but can get closer to a power found within the infection discovered by Kage. Those who embrace the Shadow rot are the Itami; a sadistic cult that continues to grow.

  The disease can be caught by inhaling the air of Kindao, a hell not of our world. The first vessels sacrificed themselves to the infection to close the gateway for the sake of their home world. But despite their heroic sacrifice, all vessels were banished from Shilon after months of violent outbreaks. Some walk away from their past and start a new life while attempting to adapt to their torment. The rest have been converted into the Itami cult, and have become the most terrifying beings among Kudao.