It depends a lot on the exact mechanics of her history manipulation. It's a possibility that she will devour the history of the fight to hide Yuuka being a fairy, but I doubt it, as she wouldn't have manipulated this fight into existence if she was just going to erase it entirely.
She might devour PMiSS's entry on Yuuka because she knows it is wrong. But that still doesn't answer why she set up the fight.
The only reason I can think of that she would set up the fight would be because something important happened in the fight. The most likely candidates being either Cirno breaking her own limits or Yuuka exposing her fairy wings.
My personal theory at the moment is that Keine was never actually the villain. All of this is just an extension of her job as a teacher.
She set up the fight to teach Team ⑨ just how powerful they could be, with enough hard work.
She set up the fight to teach Yuuka that she doesn't need to hide her wings.
She set up the fight to teach Gensokyo to never underestimate a fairy.
Now keep in mind, the plan for the fight was already set in motion before Akyuu came to her with her theory. Thus, devouring the entry was never the main part of the plan, and must just be a supporting action for the rest of it. My guess is that by devouring the entry, she removes false evidence from the public mind, and makes her point much more likely to stick.
He already posted the next panel on NND. Kazami Yuuka's entry in the Perfect Memento in a Strict Sense contains an error. That error somehow led to current events. This will be revealed in the next comic.
¯\(°_o)/¯ I'm just relaying what the author has already posted. Watch the video I linked in the last comic. 設定崩壊 = plot hole. It doesn't make sense to me either how a book of speculation can create a plot hole, but that's what potato pot is claiming. He also implies that you won't actually find an error if you look up yuuka in the memento, so maybe in this comic there's an alternate memento that is about to be eaten and remade to create the memento we know and love.
Just posting it here for posterity but I'm currently thinking that Yuuka is actually Daiyousei from another dimension or that got misplaced in time and that's why Daiyousei felt something familiar when Yuuka patted her on the head and why she hasn't been featured much, because she HAS been featured in the form of her future/alternate self.
This is also why Yuuka might want to make Cirno like her, because they were close friends a long time ago.
Plus, compare Yuuka's lower wings in this strip post #1178263 to Daiyousei's wings and you'll see that there's a resemblance.
I hope this won't spawn a discussion on how "real" fairies really are...
Those kids have really grown up, huh? (lol)Kazami YuukaMystiaWriggleRumiaHouraisan KaguyaCirnoDo you understand what you've done?The result of Sensei's education no doubt...Huh...?Sensei?DaiyouseiEntry for "Kazami Yuuka"I'll devour it for you.Hieda no Akyuu.The Perfect Memento's