Basic:

The story takes place in present-day Japan, in a world where monsters exist, hidden from humans. These monsters are not creatures with normal bodies; they are more like slimy substances/shadows that can infiltrate humans and control their minds. The goal of all these monsters is: to control humans → to gain independence → to establish kingdoms and rulers and conquer worlds. Most humans are completely unaware of their existence.

Monsters:

Monsters can enter the human body in various ways, such as through the mouth, the mind, or thought, or when the person allows them entry. However, complete control over the human mind is extremely difficult, and sometimes attempts to do so lead to the person's death. If a monster were to completely control a person, it could become independent. A person who doesn't believe in monsters cannot see them at all; even if they entered the monster world, they might only see a forest or a natural place and believe they were lost. The monster's greatest weakness is the unwavering belief that it doesn't exist. If a person sees the monster with their own eyes and yet firmly believes it's all a myth, the monster will explode, die, and be erased.

Types of monsters: 👺⚠️!!️

There are people who are half-human and half-monster. This is a rare condition. The monster within them can influence them, but it cannot easily take complete control. Some monsters are very weak, remaining inside the person only to prevent death. Others are very powerful and can cause the person to develop intense hatred for both humans and monsters.