"Sorry Anna you're not done yet!" Nina said suddenly locking her legs around Anna's neck and pulling her down hard.
Whomp!!!!
Anna hit the floor completely surprised.
Nina quickly used her right leg to get Anna in a headlock while bringing her left foot towards her sister's already abused nose.
"W-What are you doing?" Anna asked shocked. "I already did what you asked. We had a deal!!!You were supposed to stop r-remember?"
"That was with my boots sister," Nina said grinning. "Now I'm making you smell my feet! That' a completely different thing. Now why don't you be a good girl and sniff for me?"
Anna struggled but she was already very weak from sniffing her sisters boots. She didn't have much fight left in her and Nina kept her locked in that position her foot placed firmly in front of Anna's nose.
Eventually a sobbing Anna had to take a humiliating sniff of her sister's feet just to get the oxygen she needed. It smelled just as bad as her boots. Smiling, Nina kept her foot over Anna's face for 30 minutes forcing her sister to sniff repeatedly. Once Nina was satisfied Anna had sniffed her left foot enough, she released Anna's neck so that she could switch feet. By this time Anna was too weak to even try to fight back and just lay there sobbing and coughing while Nina moved her right foot into place.

After 30 minutes of being forced to sniff Nina's right foot...