The world of shadows is where "shadows" train to become "shadows". The day he had a bad feeling, he was called by the master of shadows and it was decided that he would become a certain human's shadow. His first time seeing the human world. A beautiful sight. However, contrary to that, the behavior of the humans he was attached to was always terrible. What a terrible person. I have to do something about it. Thinking this, he broke the rule that "shadows must not be found out to be alive" and started talking to humans. Then, what the humans taught him was common sense that was completely different from what he knew. "I don't know about death. Humans can't break like other things. We will continue to live forever." A story of living shadows and immortal humans.