The story follows Katagiri Inori, a reincarnated individual who, despite possessing a potent regenerative ability, wishes to live a quiet life. Inori, now a 15-year-old girl, finds this difficult as the world has recently become one where superheroes and supervillains exist.
Chapter 3 begins with Inori caught in a supervillain attack at a cafe. She helps evacuate others but is severely injured by a metal-manipulating villain with an exoskeleton. The superhero Raiden, Japan's first hero known for his speed and lightning abilities, intervenes. Inori, feigning death to avoid further attention, is surprised when Raiden saves her. Despite her severe injuries, her regenerative powers quickly begin to heal her, a fact she conceals to avoid becoming a test subject. She escapes the hospital before her recovery is fully noticed, only to break both legs during her escape.
The next day (Chapter 9), Inori is once again caught in the crossfire of a superhero-villain battle, this time trapped under rubble. Raiden rescues her again, noting their repeated encounters. Inori, having recovered from her broken legs, offers Raiden advice on how to respond to gratitude, suggesting "You're welcome" as a fitting phrase for heroes. Raiden, touched by her words and realizing she also possesses a secret, promises to protect her hidden ability.
Three years later (Chapter 15), Inori, now 18 and a university student, has become accustomed to being caught in these battles. She encounters Raiden, who has gained the title "First Generation Hero" with the emergence of new heroes. One of these new heroes is Sekko, a young man who recently became a hero inspired by Raiden. Sekko, who controls ice and snow, accidentally freezes Inori while trying to stop a villain. He is mortified, revealing he is still learning to control his powers and is overwhelmed by the pressure of being a hero. Inori, despite her own near-death experience, offers him advice and encourages him to embrace his natural clumsiness.
Inori later meets Inferno, a female hero with fire-manipulating abilities. Inferno, whose head is wreathed in flames, accidentally burns Inori's arm while trying to save her from a falling building. Inferno is deeply distressed by her mistake, revealing her insecurities and her past as a disillusioned office worker who became a hero by chance. Inori, acting as a supportive listener, helps Inferno process her guilt.
Inori also encounters Ironclad, a long-standing metal-manipulating villain, severely injured. She learns his motivation for villainy is to kill Raiden. Despite his past actions, Inori offers him a place to stay, recognizing his internal struggles.
Later, Inori, Sekko (now known as Yukitsuki), and Inferno are discussing their recent activities. Inori reveals her regenerative ability to them, explaining why she doesn't need medical attention. Sekko and Inferno, both having accidentally harmed Inori in their hero work, are relieved and impressed by her resilience. They discuss their desire to fight Ironclad, with Inori also wanting to confront him as he was her first attacker. The chapter ends with Inori reflecting on the complex nature of heroes and villains, and the societal challenges faced by those with special abilities.