Ugh it was so close to greatness...
Japan needs to fuck off trying to depict slave relationships as romantic. Shit was the last straw for me in Shield Hero, and it would have been the same for this series if not for the goodwill it had built up. They can have the MC say that he sees Nephie as an equal and have her willingly put the collar back on, but no matter how they try to justify it, it comes off as pandering to the loser otaku audience's fetish/power fantasy.