Power had been dealing with fear of the dark ever since she dealt with the darkness Devil. She couldn't be anywhere herself with being scared. She had you, Denji or Aki there with her.

You were coming home from devil hunting, tired and dirty. While everyone else got home before you. Well, you had thought But when you opened the door, you head Power running towards the door. With a scared expression

"Human!! You're home! Denji is asleep and Aki is away. I shall stay with you!"