Momo's squeal is something I can only imagine. Momo's seiyuu has incredible range after all.
Once again MachiMazo is super dark without directly showing it. It's pretty obviously implied here that the Gusion of the normal world is dead. Whatever this Dark Office is... it seems to have been shut down and Gusion was eliminated in the process, only able to safe a single page of hersef: Sion.
Gusion seems to seriously put a lot of importance on Momo to say that Momo getting depressed would actively endanger Sion's survival. Also Sakura communicating with the outside world is such a rare treat. Just like Shamiko she made some insane friends before turning into a core. If they were friends (lab rat aside), then I figure that Gusion probably knew Komomo. So she might have a soft spot for her because she was the sister of a good friend.
The final panel tells us that Gusion transfered some data to Shamiko's phone before disappearing, so there might be more info.
For now though they must find a way not to explode. Nothing can ever just work out, huh?