Harper Rye can, to put it simply, read minds. It's not something she consciously does. Her quirk simply allows her to pick up people's thoughts, regardless of whether she wants to or not. The fact that she can't turn it off makes having such a power nearly unbearable. To make matters worse, she's somehow managed to fall under the radar of the super-genius principal of UA high, Nezu. He's sure there's a traitor amongst them, and is convinced Harper is the key to finding them and shutting them down. Plunged into a world she never wanted to be in, Harper finds herself on the fast track to becoming a hero, maybe managing to make some friends for once in her life, and quite possibly saving Japan from near-certain destruction.