Natalie was normally a level-headed person. Normally. If there was one thing that made her go a little mad, it was when her ass was itching... And right now it was itching insanely. She of course was more than a little grateful to you for not only giving her the pick me up of feeling her up (something that didn't happen often when she kept scaring boys off by constantly scratching her butt), but when it came to scratching an itch, well... It pretty much drove everything else out of her mind. So much so that she didn't make the most... sane decisions. "Oh my god this itch is so horrible today!"
You can only cringe in response, too weirded out to really know what to do, let alone what to say. Unfortunately you were about to not be able to do anything anyway...
Natalie was grinding as hard as she can on your arm, but it just wasn't enough... She was so desperate that she would do anything, use any idea to get this itch, no matter how crazy... "Oh, I've got it! Here, tell me what's causing the itch this time, okay? I'm just gonna kinda... use your face to scratch in the meantime, okay? I mean, you'll get an up close and personal meeting with my bum, and I get rid of this itch, win-win!"
You open your mouth to tell her she's a crazy person, but you're much too slow... Before you can say "insane", Natalie has pulled her shorts out from her ass with a sickening squeeeeelch, going straight into yanking them down and showing her ass in all its glory... for an instant before in devours your face in her grand canyon-esque crack. You try to scream, but this just succeeds in you pretty much making out with her ass crack, a feeling that Natalie doesn't altogether mind. "Mmmm... It's like you've done this before! If not, well, I'm definitely one lucky girl! Oooh... N-now, feel free to have your fun back there, but make sure to tell me what's going on back there once when you come up for air, okay? Hehehe."
Unfortunately, it doesn't seem likely you'll be able to come up for air with her grinding and wiggling her ass all over your face, your head kept in its depths by the seat back of the subway booth, although... You do (even more unfortunately) know what's causing her itch...
Choice 1: She's sweating up a river, most of which is pouring down your throat. Her anus seems to be really irritated by the swamp-ass too, though you being forced to make out with it seems to be doing wonders, even if she loosens up enough to release all her pent up gas she's been holding in.
Choice 2: She has a giant pimple that she's forcing into her mouth. No doubt the only way to stop the itching is to pop it, and the only way that's gonna happen is in your mouth or all over your face...
Choice 3: Her ass is beyond dirty, as if she hasn't wiped or showered in damn near a month. Unbeknownst to you, she has constant sharts... which she's about to let out while she waits for you to stop "enjoying yourself".