^That Bikki is from an AU where Miku had to move away immediately after S1's noise incident that gave Hibiki her gear. As a result of not having anyone to support her during the time she was awfully persecuted for being the only survivor of that tragedy, she became grumpy and edgy (hence people took to calling her EdgeBikki)
And no, no other gears except Tsubasa and Miku exist in that world iirc because it never went past S1