When the cracks in time and space appear, the transparent person who appears along with the cracks in time and space is what we call the soul body.
What Si Min has to do is to contact the soul bodies, obtain their memories, and enter the time and space where they are.
After completing the regrets of the soul body, Si Min will gain the power called "soul breath".
Using 'soul breath' to resurrect her sister is Si Ming's ultimate goal.
