the "Alice was attacked before the arc even started" theory is interesting, but given the timeframe other victims have recovered I can't think of a way that would work. Plus, if you look at the frame when Alice's body is shown, there's an overturned teacup, suggesting she was attacked via liquid and not through old-fashioned possession (like I'm assuming happened to Yukari, Marisa, and Sakuya). Still, I'll keep that in the back of my head.
Yeah, it may seem kinda weird that Alice's possession would last much longer than Yuyuko's (if she Alice was possessed before Yuyuko), but at the same time, unlike the other victims, she had nobody to nurse her back to health. If she was possessed first, maybe that could have played a role. At any rate, while Satori detected traces of the Vengeful Spirit's thought in the Forest of Magic (Alice and Marisa's turf), it's not specified that it's anything besides mocking thoughts, and at this point Yukari is the one that is still possessed (between step 2 and step 6). If Marisa was being naughty, I wouldn't be surprised if the Vengeful Spirit decided to set her base near her ally since she's got nowhere else to go.
Although I'm not really sure about the situation surrounding Alice's tea, previous cases were as such : Patchouli got KO from the coffee that possessed Sakuya served and obviously tampered with, same goes for Meiling after drinking something that got tampered by possessed Patchouli, and likewise for Yuyuko drinking the booze brought by possessed Marisa. This might be reading too much into a mere panel, but imo if you've got a teapot by your immediate side, the chances of getting served by someone else goes down quite a bit. All previous liquid possessions happened in relation with them being served by a possessed person, which is why I was kinda thinking that for Alice's case, mmaybe, JUST maybe it was a regular old boring possession ,although her waking later than Yuyuko kinda suggests that she might have been possessed just as our attention is brought to the forest of magic. At the time, the way things stand is as such :
1 - Vengeful Spirit leaves SDM
1.5 - (???) + the Vengeful Spirit getting in contact with Marisa
2 - Possessed Marisa brings booze to Yuyuko, Yuyuko gets possessed
2.5 - The Vengeful Spirit had to leave Yuyuko in order to get Yukari
3 - Marisa and Reimu meets Yukari, Yukari later gets possessed
4 - Various events happen, Satori detects traces of the Vengeful Spirit's thoughts in the Forest of Magic
5 - Still possessed Yukari sends Marisa to the forest of magic
6 - bla bla previous argument, either repossession or Yukari ditching
Maybe the Vengeful Spirit infected her tea, dunno
And since we're talking about liquid related possession, I'm actually kinda curious about how did Marisa get possessed after the SDM arc. Regular non liquid possession is something that Vengeful Spirits are capable of doing (even brought up when the culprit being a Vengeful Spirit is revealed), but hasn't actually happened "on camera" in this manga. Although this might get clarified depending on whether
Mokou is currently possessed or not.
At most, Marisa is her pawn, not a conspirator. And besides, working with someone to hurt Reimu is the one thing Marisa would absolutely never do, no matter the reason. That alone is enough for me to dismiss the idea out of hand, personally.
I also don't think the endgame of the Vengeful Spirit is about harming Reimu, since there were quite a few opportunies to do just that previously : for example, she could have just used a possessed Sakuya (before Reimu was made aware of the possessions) to do a surprise attack featuring time powers, or used Yukari and possibly attack Reimu when she was confining herself. Even most of the previous victims didn't particularly suffer any serious harm (despite magic loss supposedly being serious for Youkai) : weak Patchouli still got to move around, while Yuyuko is plenty capable of giving a freaking piggyback : the only person who truly have been harmed at this point would be
Satori at the end of Chapter 15 : if the big bad's motives aren't about seriously harming Reimu, then Marisa getting enlisted doesn't seem off the table. I'm leaning more towards the Marisa-is-an-accomplice route because I can't picture Marisa to get manipulated at convenience, plus the things that require a proper partner that is on the ball in the more recent chapters.
While Chapter 9.5 generally seem to absolve Marisa at that point, I think there are too many suspicious things surrounding her circumstances for her to be totally clean :
- She got Reimu to be involved in this whole possession ordeal back in the beginning, EVEN exaggerated the facts (saying that Patchouli is dead) to get Reimu's interest
- Seemingly being the Vengeful Spirit's possession target (like why), with Satori suspecting her to already having been possessed multiple times
- Her intrusion in Eientei, which even coincide with the Vengeful Spirit's letter's threat
And while it's true a gap in memory may not be something Satori would be able to note per se, she would definitely be able to tell if Marisa was actively conspiring with the criminal or lying during her interrogation at Alice's house.
Still going by the angle where Marisa may be a conspirator, imo "refreshing" Marisa should not be too much of a challenge : something that seems suspicious to me happens in the start of the IN arc, where Marisa, somehow, figures out exactly that Reimu is in Eientei and even enlist Mokou's help to get just there : before this happens, an supposedly good Marisa was trying to rely on Reimu's intuition to find the Vengeful Spirit, but couldn't ask Reimu since she went to Eientei after a not-possessed-anymore Yukari told her about the Vengeful Spirit's intentions : if Marisa was going to rely on Reimu's help to find something, how did she figure Reimu's current location with exact precision ? Especially if she wasn't made aware of the Vengeful Spirit's objectives ? Extremely suspicious to me, what's with her randomly getting a bunch of highly accurate information. I think things probably went this :
- Reimu goes to Eientei
- Marisa doesn't find Reimu, may have met up with the Vengeful Spirit
- A possibly possessed Marisa goes to meet Mokou
- Possibility that
the Vengeful Spirit is moved onto Mokou, since she wasn't on Marisa anymore at the time of the captureIF Marisa is indeed an accomplice instead of just an unwitting pawn, her motives would currently elude me.
Unless it has something to do with the identity of the Vengeful Spirit who is totally M*maAs for the mysterious, unidentified and enigmatic Vengeful Spirit's motives, I think the revenge she wants to take on Gensokyo has gotta be something that's a little bit different from just harming everyone, especially Reimu (since Marisa wouldn't harm her bestie). Still not sure what her exact objective is or how her plan's endgame gonna be.