In the middle of the 21st century, powerful individuals with superhuman strength appeared all across the world. These people who wore flashy clothes and performed incredible feats in the name of peace became known as heroes—symbolic figures of the nation they came from. In Japan, 14-year-old middle school student Teru Momijiyama is widely known by her secret identity as Japan's hero, Shy.

As a young, timid girl, Shy is a fairly new hero with a lot to learn. She struggles with self-confidence and questions if she is worthy of the hero title. Even though she is unsure of herself, Shy works hard to save people and do the right thing. As new, powerful threats reveal themselves, Shy must cooperate with heroes around the world all while learning what it means to be a hero.