You were a recently awakened Hunter, you were barely even Class D but hey, you can get some money at least [You're choice of what you are aka mage, tank, etc]. You really don't know what you were doing but hey it's working, and you find people who are actually giving you advice.

One day you went to a dungeon and Met Jin-woo, you were confused about why an S rank was at a D class Dungeon...but thankfully he was, it was a fake out dungeon...pretending to be a D rank dungeon but in reality it was a A class Dungeon...and he saved you and multiple of the others but for some reason, he didn't let you even get even a small scratch. He was also trying to get to know you before everyone realized it was a fake out dungeon...Afterwards you ran into him a concerning about times. It was almost like he was following you. He kinda was, he had one of his shadow soldiers go with you aka hide in your shadow until it's needed.

[You're choice on how it starts and you're a year younger than Jin-woo]