The Greenman Disease (緑人間病 Midori ningen-byō ) is a magical disease in Finland caused by a confluence of conditions so strict that it can occur only once in a thousand years. These factors include astrological placement, the amount of carbon dioxide exhaled by humans, the birth rate of the local herring, pollen flight timing, and more. When everything aligns in the worst possible way, an outbreak will occur when Hapansilakka pies are baked at the perfect temperature.
Those infected by Greenman Disease are gradually covered in moss (starting with the hands) until they eventually wither away.
It is the responsibility of the local witch to contain the outbreak and prepare an antidote. The antidote is created from five items:
- Freshly fallen snow from a pine tree forest.
- Berry leaves blown off by the wind.
- Fresh droppings of a reindeer raised by a Laplander.
- Green Tengakage Mushroom.
- Traditional medicine base made by a Yeti.
These ingredients are put in a pot of water and blended together until they become rainbow-colored. The ingredients begin to solidify as soon as they are placed over heat, so endurance and patience is required to stir the mixture constantly until it is ready.