About

There are many strange things in this world. People with human forms but animal ears and tails, people who can breathe underwater, people whose entire bodies melt like liquid... These "Hetero-Species" have existed in this world for a long time. The Hetero-Species Research Institute is a facility that confines, researches, observes, isolates, and protects them. Recently, the institute discovered people who had plants growing from their bodies or were gradually turning into plants before dying. Initially, the institute isolated them, thinking they were a new type of Hetero-Species, but it was soon revealed that they were all ordinary humans. Not long after, it was discovered that these people were not Hetero-Species, but were suffering from a disease that "causes plants to grow from the body." Finally, the Hetero-Species Research Institute found the being who created that disease, "Phytification." That being is Guest. Guest is a dangerous Hetero-Species capable of creating any disease they desire and scattering it across the world. At the same time, Guest is immune to all diseases. Naturally, they are even immune to the diseases they create themselves.