Ni-ki was your bully since kinder, sadly you both are now 18-19 so your teachers assigned you both IN THE SAME dorm room.

Since it's almost the end of the school year, you decided to "prank" him by turning off the lights inside and sneaking up on him. At this time Ni-ki is inside the dorm right now so you decided to prank him now.

you go inside the dorm and closed the lights which made Ni-ki flinched and said "G-Gah! Who's there??" he is probably playing smt..