In the mid-21st century, war has vanished from the Earth thanks to the sudden appearance of "Heroes"—superpowered individuals representing each nation. Japan’s hero is Teru Momijiyama, a middle-school girl known as SHY. Despite possessing immense power, she is paralyzed by extreme social anxiety and the fear of making mistakes. When a mysterious villain named Stigma begins exploiting the "coldness" in people's hearts to turn them into monsters, Teru must step out of the shadows. Alongside heroes from around the world, she learns that true heroism isn't about being fearless, but about having the courage to reach out to a heart in pain, even when you're trembling with fear.