Post-nuclear Earth is barren, and life can't survive on the surface, so the few remaining people have lived under-water waiting for their time to be able to go to the surface. Amamiku and her faithful computer guardians, Pyron and Mayzamik, guard the seeds that contain the DNA for life and re-growth on the surface when the air is breathable again, but not everyone wants that to happen.

Individual pieces of human emotion usually take form as flowers known as Fragments. The select few who possess strong enough Fragments can become Reflectors, beings who equip specialized rings that allow them to connect their thoughts, memories, and emotions to those whose feelings waver. There are two types of Reflectors—those who wear blue rings to protect those falling into depravity by preserving their Fragments, and those who wear red rings to prevent negative emotions by stealing the Fragments of those who begin to develop severe woe. Despite wanting to socialize with people around her, transfer student Ruka Hanari's shy and introverted personality always gets in her way. In a chance encounter, however, she bumps into a woman who happens to drop a blue ring as she hurries away. Unable to return it, Ruka brings it back with her to her dorm. There, she meets the outgoing Hiori Hirahara, who also has a blue ring. They find themselves in several conflicts against red Reflectors, slowly realizing the true power of the rings that they hold. Now striving to become Reflectors themselves, Ruka and Hiori must learn to work together and become stronger so that they can save not only the people around them, but also themselves from the emotions that hold them back.

Second-year high school student Yatora Yaguchi is a delinquent with excellent grades, but is unmotivated to find his true calling in life. Yatora spends his days working hard to maintain his academic standing while hanging out with his equally unambitious friends. However, beneath his carefree demeanor, Yatora does not enjoy either activity and wishes he could find something more fulfilling. While mulling over his predicament, Yatora finds himself staring at a vibrant landscape of Shibuya. Unable to express how he feels about the unusually breathtaking sight, he picks up a paintbrush, hoping his thoughts will be conveyed on canvas. After receiving praise for his work, the joy he feels sends him on a journey to enter the extremely competitive Tokyo University of the Arts—a school that only accepts one in every two hundred applicants. Facing talented peers, a lack of understanding of the fine arts, and struggles to obtain his parents’ approval, Yatora is confronted by much adversity. In the hopes of securing one of the five prestigious spots in his program of choice, Yatora must show that his inexperience does not define him.

With Tomura Shigaraki at its helm, the former Liberation Army is now known as the Paranormal Liberation Front. This organized criminal group poses an immense threat to the Hero Association, not only because of its sheer size and strength, but also the overpowering quirks of Jin Twice Bubaigawara and Gigantomachia. As new intel from the covert hero Keigo Hawks Takami confirms that Shigaraki is nowhere to be seen, the Hero Association decides to strike the enemy headquarters with a surprise attack using the entirety of its assets—and the UA students find themselves on the battlefield once again. As the fight rages on, the unsuspecting villains must regroup and push back, but the brave heroes are determined to eradicate every last one of them.