14-year-old Teru Momijiyama is Japan's hero representative, who goes by the hero name "Shy" as a result of her extreme shyness. After being chosen to serve her country, Teru is invited to make an appearance at an amusement park to give a public speech. However, her shyness ends up boring the audience to the point that she leaves the stage in embarrassment. More misfortune continues as she tries to save riders from a broken roller coaster, with one girl, Iko Koishikawa, suffering severe injuries in the process. The public blames Teru for failing to properly rescue Iko, which causes Teru to slip into a deep depression, lose her powers, and go into isolation for a month. Her closest friend, Russian hero Spirit, appears to her to give her encouragement and try to make her understand that she can't please everyone. With her friend's words in mind, Teru turns her attention to a burning building. She is able to muster up the courage to transform back into Shy and rush into the fire to save a woman and a child. After the series of incidents, Iko is later transferred to Teru's school to make things easier for herself due to her injury, as the school is closer to her home. She thanks her for saving her, and the two get to know each other and become friends. Now, with renewed determination, while improving to become a better, more confident person and hero, and fighting alongside her hero colleagues from around the globe, she defends the world against Amarariruku, an evil villainous organization that appeared soon after the world was at peace after the threat of world war ended. The group was created by Stigma, their leader, in order to further his dreams of an ideal world made just for children.