Eventually, Nina patience pays off as she’s hears the vacuum cleaner like sound of Anna breathing in deeply trying to take in whatever air she missed while she was holding her breath. Unfortunately it isn’t fresh air that Anna is getting but the odor of her sister’s overworked feet that fills her lungs. Of course her body can’t handle it and the unfortunate assassin shakes and coughs violently trying desperately to reject the polluted air but can't because Nina continues to press the boot against her face.

The blonde assassin giggles with delight and teasingly pats her sister’s head.
“Good girl Anna,” She says chuckling and taking the boot off of her nose. “For you to sniff that hard means you must really enjoy it. Do you want more?”
“MMMMPFFFF” Anna says through the gag angrily shaking her head trying her best indicate no.
“You do?” Nina says feigning a surprised expression “Ok. If that’s what you want.”
As Anna shakes her head vigorously trying to get her sister to stop, Nina once again presses her boot against Anna’s face causing the younger sister to scream through her gag.

What does Nina do next?