I was somewhat hoping it wasn't going to be the very obvious choice, though I guess either the voice was a red herring or there is at least two different girls from the company interested. Honestly if it isn't two people I'd be slightly shocked considering the manga literally had Shinbashi in direct view of Shibuya (the main ex-sister-in-law female) talking to Ayase.
Well, at least we have the full name of the sexual assaulter, Shinbashi Kurumi. Not a huge surprise considering how she's basically grabbed him unawares twice before now on the trip.