Still so much from the agency feels so sketchy. In the case of Hinagiku, they didn’t want to search for her or spend resources on her because they viewed her as a liability. It is the good old-fashioned way: the company wants you to dedicate your heart and soul to them, but when you are not as much of a use to them, they will throw you out without any hesitation.
As far as the two sisters are concerned, there is their tradition of getting married. Thus Ruri’s husband would take over guard duties. Though I do wonder if he is capable of also doing the work that Ayame does. From what we’ve seen in the flashbacks of the sisters, it feels like they have been joined at the hip, so the two of them going their separate ways seems like it would be hard for Ruri as her Ayame is ingrained in her day-to-day life so much. It is just a reality she has to endure.
Ending on that cliffhanger is quite cruel, to say the least.