I would go so far as to say that you are somewhat intended to romance the RO in each book, and the narrative goes a bit wobbly in places if you don’t. My guess is that there will be an actual lock-in choice close to the end of the series.
Book 5 was phenomenal. Easily the best in the entire series, that’s my opinion, anyway. I read the first book back in late 2015 and I’ve been hooked ever since.
And honestly, that reunion with M in the final chapter really does cement just how strong the bond is between them and the Ronin and the lengths those 2 will go to to save one another.
This series is exquisite and the author really did outdo themselves with this one.
The emotional payoff in this series is incredible. No doubt one of the most accomplished works here, and by far the one that feels the most like an adventure or epic.