Katsuhira Agata is a calm and withdrawn adolescent whose perception of pain has almost completely evaporated. Chidori Takashiro, his buddy, can only vaguely recall the days before Katsuhira underwent this drastic transformation. Katsuhira's quiet and complacent manner has now made him a continuous target for bullies, who exploit him for exorbitant sums of money. Their blows, however, merely manage to make him blink, since even emotions are beyond his grasp. However, one day, Katsuhira, Chidori, and four other teens are kidnapped and forced to join the Kizuna System as official "Kiznaivers." Those who participate are linked by pain: if one member is hurt, the others will endure an equivalent degree of anguish. These people must be used as test subjects and scapegoats.