@fgsfdss
That's Takebayashi. (Chapter 34, page 3)
She was a classmate (class rep) that went on the school trip to Kyoto 5 years ago with Fuutaro. It seems that Fuutaro had a crush on her but during the trip he sees her coupled with a classmate and he felt like the odd man out. So he made the excuse to separate from the group and he went off on his own. And that's where, at the bottom of the steps, he ran into the incident of the crazy girl accusing him of taking pictures of her involving the police. You see in that scene he was self conscious of the giving up the camera because in the camera he has pics of Takebayashi. And that's when Yotsuba shows up to defend him.
A coincidence that Takebayashi ran into the quints eh?