I LOVE this series so much, but this is definitely my least favorite volume of the series thus far.
It was not badly written as Koyou is amazing as ever and I admire her determination to never stop looking for a cure! Plus when she feels extremely certain of what is happening and why the sickness is spreading, she learned from her interaction with her last patient (and what a wise man told her) and changed how she would have initially handled the open hostility towards her.
The reason I bring that up is because I think it was very critical to see how different Koyou is from Shoushin when it comes to taking care of others. They are VERY similar as it's been pointed out before (and in this volume specifically), but as it was shown in Koyou's actions at the end, she isn't like him.
Which is a relief because Shoushin has always rubbed me wrong and seeing his backstory, it definitely explains why. I think it's "villains" like him who are some of the scariest and most compelling characters there are because while I really want Koyou to stay away from him, I don't utterly dislike him either. He makes me uncomfortable and really hate how we see that he is "playing god" of sorts and "giving out" trials to people to see how they'll react/respond. Oh, how I hated that! It's not his place to do any such thing, but it explains his motivations very well.
Lastly, I will say that this volume did have an extremely triggering moment that left me very unsettled when I read this yesterday. TW: There is a GROWN man who makes it known that he wants Shoushin, who at that time is a child. A CHILD. Someone could say he was a preteen, but that doesn't excuse that this man obviously did things with a CHILD in bed and has some kind of one-sided lust/"affection" for him.
I was VERY upset about it even though there is nothing intimate shown outside of him holding Shoushin's hand, it deeply deeply bothered me nonetheless.
I will definitely still keep reading the series because I love it, but I know this is the only volume I will only reread the beginning and the end of because the middle is too upsetting for me.