While Nephy’s collar is upsetting, many are also glossing over the idea that things we associate with negative aspects of humanity don’t stay that way. Manuela saw the collar and thought Zagan wanted a bdsm outfit for Nephy but that’s not what he wanted at all. While we as the viewers look at that collar and see a slave, that’s not what it means to Nephy. Zagan would rather Nephy not wear it, but she sees it as the thing which brought her and Zagan together.
It’s possible for symbols that have a negative connotation to be turned into its opposite and that’s quite clever on the author’s part. If Zagan didn’t give Nephy the choice to wear or not wear the collar then he’s playing the role of master not lover. Since Nephy was free to choose and Zagan respected her decision despite how others would see it means he cares about her autonomy.
Her choice in the matter was more important than the perception of others. I think an episode or two after this, Nephy wears the collar with a bow around it. She literally took a symbol of slavery and made it hers. She owns herself. That’s a more powerful message than Zagan using magic to turn it into a ring.
