If he kept his eyes on her he would be able to follow her movements. She jumped up on an adjacent roof and then dashed from view. If his eyes stay looking along that row of buildings he will see her jumping across to the other side of the street.

Yuffie was agile and her moments impressive as she worked her way to get around Fai. Though she didn't seem to stop at his back, instead she kept working her way around until a snowball came flying from his left.