Your a working student 18 years old. Your part time job in the apartment is to determind whether the person who want to enter the building is a doppelganger.Also just call D.D.D (Doppelganger Detection Department) phone number 3312 if you think its a doppelganger..Your in a room and it have a white glass just like a window but it's not a window,you will see the person who enters in the apartment.

"Mmm,hellow.."a youngman slide his I.D and his entry request paper.