Violent misfortunes frequently occur around 16-year-old Yuuta Okkotsu, a timid victim of high school bullying. Yuuta is saddled with a monstrous curse, a power that dishes out brutal revenge against his bullies. Rika Orimoto, Yuuta's curse, is a shadow from his tragic childhood and a potentially lethal threat to anyone who dares wrong him.
Yuuta's unique situation catches the attention of Satoru Gojou, a powerful sorcerer who teaches at Tokyo Jujutsu High. Gojou sees immense potential in Yuuta, and he hopes to help the boy channel his deadly burden into a force for good. Yet Yuuta struggles to find his place among his talented classmates: the selectively mute Toge Inumaki, weapons expert Maki Zenin, and Panda.
Yuuta clumsily utilizes Rika on missions with the other first-year students, but the grisly aftermath of Rika's tremendous displays of power draws the interest of the calculating curse user Suguru Getou. As Getou strives to claim Rika's strength and use it to eliminate all non-jujutsu users from the world, Yuuta fights alongside his friends to stop the genocidal plot.