It’s kinda interesting that Yukari, who initially claimed to want to protect Kosuzu from Reimu, would somehow get Kosuzu to be in a position that is very much like a target for Reimu. Anyway, while Yukari might seem like a shifty duplicitous trickster, whenever she gets involved, she usually has some kind of goal that serves Gensokyo’s well being on the long run, while not necessarily as beneficial for the involved parties. As far as this current arc goes, I’m of the opinion that Yukari is targeting Kosuzu’s night parade scroll. What kind of plan exactly and what she might want to do with it, I dunno, but it’s possible she want to have some control over it or straight up take it out of the circulation :
One of the recurring theme of FS is youkai politics, but when it comes to youkai relations and their standing in general, power is key : the strong rules, the weak are just there. Youkai politics is, from what I can tell with FS and DDC, essentially 2 things : Youkai-on-Human politics, AND Youkai-on-Youkai politics.
The Youkai-on-Human politics is especially simple : Humans MUST be at the bottom of the barrel and stay there : Human fear is needed, and Youkai must be strong enough to command fear.
And for the relationship between the Youkai or their own politics, simply put, the strong rules (which is pretty much a key point in DDC) : for example Yukari is the strongest youkai in Gensokyo, so she call the shots, do whatever she wants and get away with it.
But the thing about strong youkai in Gensokyo is that it’s not like they pop out of the blue : most of them have been there for quite a while, and as people who are fairly aware of how things roll in Gensokyo, they don’t cause trouble (or they do but within the rules), and as for the minor / weaker youkais, they cannot do anything that go against the rules, no matter how much they want to, else they’d get put in their place (pretty much ISC ?)
Basically, Gensokyo have rules : the strong respect them so everyone else better follow suit.
So… what’s kind of problem could have been introduced by FS ? The night parade scroll.
On one side,It can empower youkai and even give birth to tsukkumogami, so it’s already not too power balance friendly, as far as youkai-on-youkai politic goes : it could help whatever youkai hold it rise up in the power hierarchy : it could be problematic if it ended in the wrong hands.
And on another side, it contains an especially powerful youkai : if the strong rules the weak and guarantee order by pretty much being some kind of dissuasive force for whoever want to break the rules, a STRONG NEWCOMER who is NOT necessarily familiar with the rules of Gensokyo and might not be kept in check is obviously going to threaten the order in Gensokyo.
One key point is that the Human Village needs to be preserved so pretty much everyone (youkai) who know what’s good for them will make sure to do so : interference (the bad one obviously) with the Human Village, for youkai, is obviously a taboo. Yet the very nature of youkai is such that they must be at odds with humans : they are enemies. Gensokyos’ youkai know the relevance of the human village so they won’t do anything too rash towards it… but what of the youkais who are not familiar with that ? They are going to be, like, some sort of danger.
Considering all of that, It should be pretty obvious that the night parade scroll is an artifact that can put the power balance in peril.
My guess is that whatever plot Yukari is cooking revolves around the night parade scroll and that such plot requires Kosuzu to a certain extent (else she wouldn't involve her). Where exactly does Kosuzu comes into play in that, I dunno. At any rate, I can't clearly see how Yukari is protecting Kosuzu with all of this. Maybe she's just a stepping stone towards her objective ? We'll see what this is all about in the next chapter(s ?), I guess. Besides, there's still a question that begs to be asked regarding what exactly happened between Kosuzu leaving with her Youma books and her coming back at the Shrine.
At any rate, this chapter kinda answer the "what's gonna happen to Kosuzu if (...)" question from a while back, so there's that. Kosuzu has some crazy luck.