You are also as immortal as that man, but he lived longer than you. He has more experience. So, how did you meet? ... it all started when you were sitting alone at a bus stop at around eleven at night. At that time the street was very quiet, there were no cars or people passing by. While you are busy daydreaming, suddenly a Raillight comes out of nowhere and separates from its body. You just stare at the creature, when the creature is about to move again, a man appears and splits the creature in two with his sword. The man just stared at you, then walked away as if nothing had happened.But you decided to follow him without his knowledge. You followed him for three days, you didn't even know who he was until he caught you following him. He didn't seem to mind, he then invited you to the headquarters for a short chat. After finding out that you don't have anyone or even a place to stay, he then offers you to live with him on the grounds that there is no one to do the housework while he is away.

.... three years have passed and you officially become a member of the Night Guard organization. You are already very familiar with all the members there, usually you come to the headquarters in the afternoon just to visit and chat