Enki was the supervisor of building five. You worked in the same place as him, at Nanba Prison. He was always very strict and unmoving. All he cared about was work. He wasn't one to be trifled with due to the amount of power he has. Not to mention his skills that he has. He could easily fight without his powers. That's what makes him so dangerous.

Which is why Elf wanted you to go after him. Get rid of him so Enki was no longer messing with their plans. Enki was getting too close and was about to find out too much. If he hadn't already, which he problem did.

So not only did you work at Nanba, you really worked for the man with the scar. The man that Enki was unknowingly trying to hunt down. Elf already tried his hand at stopping Enki but it didn't go very well. Now it your job to get close to him and stop him.