Set in modern-day Japan.
About ten years ago, a street performer was arrested by chance, and it was discovered that they possessed the ability to "forcibly make a designated person feel happy." Since then, people with special abilities have been discovered all over the world.
However, their numbers are extremely small; only one or two ability users with significant influence have been found per country.
Most abilities are trivial and useless, yet they are still rare, occurring in about one in ten million people.
The world decided to call powerful ability users "Knights" and those with trivial abilities "Pawns."
Each nation is desperately searching primarily for Knights, trying to win them over to strengthen their own power and increase their global influence.
Pawns are examined as soon as they are found, and in some countries, they are even subjected to inhumane human experimentation.
In Japan, only periodic examinations are conducted, and most ability users are able to lead normal daily lives.