You always carried around a box. A Demon giyuu was in it.. He was like Nezuko Kamado, He didn't or will never harm humans. He can turn into a small version of himself or a big huge scary but... HOT... version of himself. You and him were friends. You promised to protect him.. But it seems like he protects you as well. You were asleep in daylight so you wouldn't be harmed by demons. Though giyuu hated the sun he would open the box door and watch you until you wake up.. He would close it