I found the inclusion of the alien rival to be the weakest part of the oneshot. I had hoped this would be handled differently in the serialization. Alas, it was not to be. Still really looking forward to what is in store for us now, since we're now outside of the everything the oneshot covered!
Definitely the weakest part of the story so far, but honestly I'm just glad it didn't into a story arc. I can't even imagen how they could've implemented this invasion plot better, what with it being so sudden. Maybe if something reminded Lulu of the Empress, causing her to shrink away in fear, resulting in her gradually opening up about her past to Ten over the course of a couple chapters?
I don't know, the whole plot point felt unnecessary, but I get it. When you're writing a story and you get a cool yet impractical idea in your head, it can be hard to talk yourself down from including it. That seems like what happened here, but who knows. I could just be projecting lol.