This depends on who was killed by Ryoba, I decided to do a randomized wheel spin to determine who was killed after Sumire and who was killed last since it's similar to the FNAF storyline. We already know Sumire was Ryoba's first victim, this just randomizes who she killed.
Second victim: Ai
Third victim: Sumiko
Fourth victim: Honami
Fifth victim: Moeko
Sixth and final victim: Ritsuko