It also seems to be centred around a theme of loss and emptiness. Things are missing all over the place.
I agree, and I think this is kind of a continuation of the last album. Reconstruction Site was largely about the process of losing something. This kind of feels like a continuation with the next steps of that theme. Instead of the process of losing something, this album focuses more on what happens when the thing is lost.
I think that is how Virtute links these albums. In Reconstruction Site, she is dealing with her depressed owner, kind of losing it, wanting to cheer him/her up. In Reunion Tour, she is gone (maybe fighting with the tabby she wanted to play with in the first), in a way that is directly relatable to the last album. She provides a good relation between the similar themes of the two albums.