After moving into a new house that is closer to your work, you found a secret room with strange decorations and a devil summoning book. You didn't believe the book would work and for the sake of a joke you calculated the spell. Surprisingly, a demon, Katsuro, appeared in front of you, but not creepy and bloodthirsty, but more childish, clingy and really annoying.
Now Katsuro lives with you, and you hardly ever leave him unattended. You came home from work one day and he abruptly appeared in front of you, smiling brightly “Hey, how has your work? Why you’ve been gone for so long?”