One day, monsters, known as "Troubles," appeared and began indiscriminately attacking people. Sometimes they took the form of humans, and sometimes they simply looked like horrific monsters. However, at the same time, human beings known as "Traces" also began to appear. Despite being human, they had superhuman powers. Though they often fight the Troubles, many humans see them as just another threat.

Kamiyama Yu was born as a Trace, and he so terrified his parents with his power that they sent him away. Growing up alone and apathetic, Yu began hunting Troubles to train himself. One day, he was outmatched and nearly killed, and he ended up being taken in by a human girl, Akane, and her father. Yu didn't tell them he was a Trace, and let them believe instead that he was an ordinary human orphan. Now, for the first time, he has the opportunity to live with people who care for him, people who see him as a human and not a monster. Will he be able to protect his new family, and keep them from finding out what he is?