From publisher blurb:
In this system-agnostic Sci-Fi supplement and love-letter to Mushishi by Yuki Urushibara, your characters play as frontier doctors called Kaichū-Shi or Parasite Masters.
They'll exploring dark forests and researching parasitic organisms, known as Kaichū, that exist in a classification somewhere between plants and insects. Heal colonists and blue collar workers who fall sick with mysterious ailments, exhibiting symptoms that vary from minor to life-threatening.
Many of the organisms are only visible when viewed through specific spectrums of light. Some only partially exist in this universe. When viewed, they are often semi-corporeal, ethereal creatures that bend light around them as they float and crawl around.
To play you'll need:
This Pamphlet
A set of polyhedral dice (specifically d10's)
The TTRPG of your choice
CW: This module contains elements relating to sicknesses and treatments and may not be suitable for all audiences