Personally I don’t agree that this series deserves a 1. I’d still rate it 6 even with this arc, and if the spoiler ends up happening and the series ends there. There are so many more worse mangas out there, and so many mangas that has tedious arcs (RAG for example) that goes on forever.
I don’t regret reading this. It had a good premise, and the first half was decent. Just feels like that the author didn’t know where to take the story or how to keep developing the characters which ended up with this arc. One can only hope that the author has a better goal for their next story before they start writing and publishing it