That's some femme fatale, for sure. Were those masked dudes (decent men, trying to avoid spreading Covid-19) working with her or not? Hard to say. It seems to me Kageya could be working with them, taking some rich dude from the party, drugging him, pushing him out of the carriage, and the dudes would then kidnap him for ransom. Or maybe they are working for someone else, investigating the incidents just like Shirayaki & Co. However, they called Kageya lady, which seems to suggest a level of respect.