The fictional Japanese city named Sugomori City is built on reclaimed land. But as the years go by, the city's population is decreasing. One day, Sonosaki tells her classmate Katsuhira: "You have been selected to be a Kiznaiver." The Kizuna System, which allows Katsuhira to share his wounds, connects him to the classmates whose lives and personalities completely differ from his. The Kizuna System is an incomplete system for the implementation of world peace that connects people through wounds. All those who are connected to this system are called Kiznaivers. When one Kiznaiver is wounded, the system divides and transmits the wound among the other Kiznaivers.
Yūki Ōjima attends Takafuji Private Academy, a large school with over 6,000 students, where he is a member of the Food Research Club along with seven others, including his childhood friend Chisato Sumiyoshi. The members leisurely spend their time in the club doing very little. When the election for the next student council president comes up, the front runner Satsuki Shinonome proposes that clubs which have no merit should be sorted out and abolished. The Food Research Club seeks advice from the current student council president, Yakumo Mōri, who suggests that Yūki run in the election as an opposing candidate. Yūki learns about the issues facing the school and decides to run in the election.
Enter Sentan, a lush, tranquil island encased in war between the military and those with Hiruko, known as X'amd. On one of these warlike days, Akiyuki Takehara heads off to school and gets caught in a raid by the creatures. Through a series of events he is transformed into a X'amd, and with the help of a Tessikan woman Nakiami along with his highschool friend Haru, Akiyuki is forced to learn to live with the Hiruko or faces the danger of losing his self-control and turn to stone.
Ryuu Yamada is known as a delinquent in his high school; he has been bored of classes after one year of attending school. One day, he accidentally falls from a flight of stairs onto Urara Shiraishi, the ace student of the school. Yamada wakes up to find that he has swapped bodies with her! The two try to reverse the change and discover that kissing triggers the body swap. On the suggestion of student council vice-president Toranosuke Miyamura, they revive the Supernatural Studies Club. The club encounters other "witches" with different powers that are activated with a kiss!