The story takes place after the end of Trace 1 and revolves around Han Sihyun, an investigator of the National Investigation Service (NIS). In attempt to find a way to coexist with "Troubles" instead of killing them, Sihyun frequently proposal to the board of NIS to approve a research on communicating with "Trouble." But after getting his proposal rejected yet again, Sihyun accidentally captured "Trouble" while he was drunk and decided to illegally experiment on it. Though communication seems impossible at first, Sihyun and his "Trouble" slowly begin to close the distant between them and form a bond together.


The story set in the contemporary South Korea. Some 30 years ago, unidentified creatures appeared out of nowhere and have attacked people. They have caused massive destruction wherever they go. The monsters are called "Trouble", and get the world have fallen into chaos. Along with the first appearance of the "Troubles", some number of humans were born with or acquired supernatural abilities. These mutants called "Trace" are the only ones who can fight off the "Trouble". The "Trace" are also considered freaks and generally shunned by the community because some of them misused the powers for their own interest.<br>
<br>

The plot revolves around two main characters. Sa Kang-Gwon, a high school student born as a "Trace" who attempts to hide his ability. The other is Kim Yun-Seong, who acquired his "Trace" abilities during his early 30s. Soon after the acquisition, his wife and daughter were taken away from him for experimental purposes.

Tags