Unrevealed Secrets

Jeon Jeonnguk is a person not to be messed with, he's ruthless and will never hesitate to kill those who stand in his way... so why.... why can't he kill a single woman who can't even protect herself, as if his whole body is preventing him from hurting her in every way? He's frustrated, he doesn't know what to do, he never felt anything like this before... just what is happening?