Pretty sure that'd be Cloud behind her, roughing her down to get his Materia back.

AMONG OTHER THNGS.

I'd her materia. Or actually I guess I mean *his* materia. Wait, no I don't. Um... I'd his materia, if she were still holding on to it.

...y'know what, forget the whole thing.

...Put 'em back.

Artist's comments:
"ク「そんなわけないだろ」　ユ「ハハハ…；」　ク「まだ足りない」　ユ「残りはホント、もう無くて…」　ク「…仕方ないな」　ユ「え、ちょ、待て待て待って！」　…なぁんてな。"

Translation of dialog to the best of my ability:

C: 「そんなわけないだろ」(You don't know about these.<imp:You don't know where they are or if after: You honestly don't know where they came from or what they were doing in your shirt.>)
Y:「hahaha…；」
C:「まだ足りない」(This isn't enough.<imp:we're still missing more than just these>)
Y:「残りはホント、もう無くて…」(really, I don't have the rest)
C:「…then I've got no choice.」
Y:「uh、wai、waitwaitwait！」

I should mention that I don't know if this dialog takes place before or after what we see here.

Artist's comments:
"ク「そんなわけないだろ」　
ユ「ハハハ…；」　
ク「まだ足りない」　
ユ「残りはホント、もう無くて…」　
ク「…仕方ないな」　
ユ「え、ちょ、待て待て待って！」　
…なぁんてな。"

translation:
___
'Cloud: "Like hell it would!"
Yuffie: "Hahaha... (sweat)"
C: "That's not good enough."
Y: "There really aren't any more, though..."
C: "Guess I have no choice, huh?"
Y: "Hey, wha-! J-j-j-just hold on a sec-!"
...or something like that.'
___
I think it's supposed to take place before, and during.

Hah. I'm going with Bansho's translation, and it's probably during... and hinting he's gonna be searching her... lower clothing next.