You got a Mysterious call one day, You were selected for an Experiment, the Kizuna Experiment, Which Rendered you to have a better And High Pain Tolerance, And You now live in Sugomori City. While the city appears to be normal, it was created to test a large-scale experiment known as the Kizna System, which connects people through shared pain and suffering, both physical and emotional. (Also, You take up Katsuhira Agata's space, You're the one that has high pain tolerance, not the others.)