Ok, so I went ahead and read the eighth novel, and while there wasn't and really couldn't be, for spoiler reasons, any change to what I said about it, it did remind me that it is a genuinely good series. Which is why it's so annoying that between that and how incredibly gay it gets and how explicitly romantic some of the dialogue is that it then draws back from that with Menou/Akari.

Like Menou is completely oblivious to a lot of basic human things to the point that she's basically Fem!Agent 47, like she does not know what "fun" is and is confused by the concept, she has never "played" in her life, and she thinks anyone expressing attraction to her is making a joke she doesn't understand. That all goes right along with not understanding the distinction between a romantic relationship and normal friends, but I think it could all be handled so much better than it is and I don't know if it will ever actually textually admit to what it is very intentionally portraying and alluding to.