Dorothy originally intended each chapter to be ~24 pages but at some point couldn't help making them longer. Chapter 17 puts volume 3 at 164 pages(+extras), so it's potentially the volume finale unless 18's a short one. And it sure feels like it.
The construction of this chapter as the festival's climax was exceptional; very cinematic with Michi and Ange counter-posed multiple times and Sayaka saving the day. As well as returning to everything established this volume (Karasuma, the idols, Michi wanting to protect Aizawa, Michi feeling like she has no role in the world).
I was a little worried we'd get some answers but thankfully nothing makes sense still. We're not ending anytime soon. But at least after 17 chapters Michi finally realized she's the protagonist of a yuri manga.
Michi
As the story progresses, it's interesting how Michi has begun to feel equally trapped and in need of rescuing. Seems like Aizawa really was that special to her that deleting her emptied Michi out. Yet in spite of being stuck in such a victim role, I admire how she always remains concerned for Aizawa's well-being. Whenever Aizawa gets scary or dangerous, even though Michi's the one getting spooked, she quickly worries how that made Aizawa feel. It's very sweet, even if she keeps failing her standards of protecting her.
Maybe I get too absorbed in fiction but her running around was pretty emotional (along with Young Michi's apology). Admitting she's desperately afraid of losing what's most important to her all over again, even if she doesn't understand it. She's put up a good fight denying the love between her and Aizawa but it looks like that's over with. Very excited to see how she handles admitting she's fallen for a ghost she's still (badly) pretending to ignore.
In some of the AAA stars you can see the first 2 AAs are separate from the 3rd; it really does makes it look like it's actually M A (Michi Aizawa), most notably on page 26. The only issue I see with that theory is Michi still calling her girlfriend by her surname instead of Honami, but she is a dork.
Aizawa
As for her other half, I do think Aizawa's more aware of what's happening than Michi is. If Michi's trapped, someone needs to step up to be her protector too, and Aizawa's the one comforting Michi in the end.
The kiss seems out of place if she's been unconscious through the whole dream, but natural if she understands Michi fought her way to find her. She obviously knows about Young Michi, having "spoken" with her twice, and is implied to remember their relationship before she died if she's hurt by being forgotten. Michi even comments Aizawa should have figured out by now she can feel her touch from her reactions. Either Aizawa is that dumb or she's just playing along and sometimes can't control her urges.
Also more fuel for the "Aizawa is actually her pet cat and Dorothy is ripping off Ghost Trick" crack theory.
Sayaka
Speaking of just that dumb or playing along, it's wild how in 2 chapter's Sayaka's changed from comic relief dumbass to tragic hero. Like I said last chapter, there were always hints of Sayaka being more perceptive than she let on, but I never imagined it was that drastic. She likely is Michi's opposite, trying not to upset ghosts by normalizing them as people like anyone else. And so far much more effective at it.
I really hope she's able to tell Kasumi the truth at some point before the story's over. There's a bit of setup with Kasumi knowing Sayaka and Michi see a fairy (Aizawa). And I'm certain Sayaka will get an arc of her own. Between the introduction of her unique properties, the health risks of using her own blood for protection, and the foreshadowing of how her kindness and boldness in dealing with ghosts will get her taken advantage of, it seems like she's bound to get hurt at some point.
Karasuma/Grandma Horimitsu
My mental character chart re-arranges. Karasuma's close to Sayaka, not Michi, though by faintly recognizing Michi's mark she must have encountered her before. And in chapter 13 she did know Michi by face and name, swearing not to fail her a 2nd time.
Still one big mystery character. It's anyone's guess why she's taking lessons from Sayaka's grandmother; maybe it helps with exorcism. Her crows did have a unique brushlike quality to them. But it sounds like she frequently talks to Sayaka about ghosts.
I theorized back in chapter 13 Karasuma had some kind of pact with a ghost herself, since she struggled to get past the school's anti-ghost barrier. Sayaka would be different, having a deep power that comes from her blood. Just glimpses of the world of spiritualists so far but we're sure to learn more.
And I'm unclear on how much Sayaka's grandmother knows about that world. Typically when you have powerful magic blood, it's your bloodline. She calls all that talk of ghosts and curses lies, but it's worth noting no one mentioned ghosts. Sure, those 2 likely have these talks often but on a meta level there's still some suspicion cast on the elder Horimitsu. Is she just pretending these things aren't real for her granddaughter's sake, and is that also what brings Karasuma to learn from her?
Another little detail: back in volume 2's extras Sayaka said her treasure was the kimono she got from her grandmother. They definitely have a close bond.
Ange(?)
I maintain this is 100% a case of possession. We know Ange the least of the 3 idols, but it's clear her professional demeanor dropped the moment her sickness kicked in and her eyes went blank, like Kasumi getting possessed. And Dorothy highlights it with the change in familiarity: Tear-san to Tear-chan (which reverted for some reason this chapter) and Honami-san to Hona-chan.
Whatever this ghost is seems awfully close to Aizawa? If she's the studio ghost, she was angered by them forgetting her. But at the same time she needs Aizawa to be fully dead? Impossible to make sense of this yet but she's clearly our primary antagonist for now. (Even if I kind of feel bad for her after getting kicked out so quick. If she hadn't showed up at all and triggered Sayaka's spider-sense Aizawa might have died naturally.)
Wild theories include her being another half of Aizawa herself, or her being the secret 5th member of De:Lphinus that fills out the crack Sailor Moon parallel.
Also yes Theia is Tear. I got bamboozled hard. I might go back and correct previous chapters.