Sorry, this will be long, but I have a lot of thoughts I need to get out.
I really tried to like this series. I defended it for awhile, and I thought it couldn't be as bad as SSiB, my previous least favorite Touhou official manga. As one might expect from my pfp, I am very attached to the Komeiji siblings. I also really love mysteries, especially if they're murder mystery themed like this one. But I found myself enjoying it less and less as it went on, and Chapter 29 finally killed the series for me. I'm so disappointed by how Satori is treated in the series named after her. You would think that being the titular character might make her at least A main character, but she's not even a secondary character. She's practically a glorified extra, which sucks because her ability that previous caused her to be hated by everyone in-universe could have been used to show her becoming loved for the exact same reason. Even worse is that the series is now fighting for who actually can be a main character between like five different people, and none of them are the titular character. Yeah, it was great seeing Flandre again, but why is she still playing such a large role in this when it's moved so far past the Scarlet Devil Mansion?
And as much as I love Reimu and Marisa, I can't deny that they are quite possible the WORST characters to lead a mystery story. They have no interest in figuring out the why, the how, the who, any of the things that make a mystery compelling. They just want to end the incident and be done with it. That works fine for games where it's not trying to build up a mysterious and tense atmosphere, but for something that's meant to be a mystery story, I can't help but wonder why they're so involved. Especially since this manga is probably the worst offender of a trend I've noticed recently of Reimu canonically losing at pretty much everything.
Characterization also started out pretty strong. We saw Reimu and Marisa being concerned about those around them instead of just themselves. Flandre was given interesting character shading that made her seem less violently unhinged and more of a standoffish devil-may-care kind of anti-hero. Orin was in the story at all (seriously, how long has she been tied to that damn tree!), and Satori was an active and key player at first. Now, Reimu and Marisa are in this pretty much just for themselves (which circles back to my previous point), Flandre has fully reverted into pure fanon characterization, actively UNDOING development she had (and don't worry, undone progress is going to be commented on more). And Satori is a glorified extra, which is insulting not only because the series is called Foul/Cheating Detective Satori, and not only because she's the only character who seemingly IS interested in the who, the what, the why, the how, and so on. And, she's the only one with a decent chance of solving things. It would be so much more interesting to see this from her perspective.
While it's not really here as much anymore, when the artist switched, I noticed a lot of very out-of-place comedy for a story that seems like it's trying to present itself seriously. I know comedy is nothing new to Touhou, but the story had established itself as a far more dramatic and serious story with the first artist, and I don't think it's unreasonable to want the same tone to carry throughout an entire story so it can be consistent.
Of course, what hasn't stopped is the awful pacing. This story has such a huge issue with padding that it genuinely makes me sad. It's gotten to the point of actively undoing progress, possibly best demonstrated in the most recent chapter (chapter 29 at the time of writing). The story drags itself out for so long that any time progress is made, you'd better not expect it to stay, because it WILL change anything before that progress means anything, and then we're back to square one. Like, for example, how we finally figured out who was possessed (Kyouko) only for the pacing to drag on so long for no good reason that it changed before that information could mean anything. Even more insulting, the person now possessed is the titular character, who by all accounts, should have been the story's heroine.
I also can't get into The Jailbreak King at all. I mentioned before that Silent Sinner in Blue was my previous least favorite official Touhou manga. There are two reasons for that, both present here. One is the aforementioned pacing and padding, and the other is the ridiculously OP antagonists. Yorihime made me enraged with how ridiculously flawless she was, as she was completely untouchable. The new villain Mizuchi is that but worse. She is pretty much entirely invulnerable and always 10 steps ahead of everyone. This could make for a good mystery premise if we got to slowly chip away at that lead, but again, the pacing and padding makes that impossible. Not to mention all the lore it messes up (like the most powerful youkai in the setting being incredibly easy to possess), or the fact that it makes no sense why Mizuchi can get away with possessing one of the sages and no one is particularly bothered by it.
I can't even be mad about the premise. It is such a cool premise. Like I said, a character who is hated in-universe by everyone for her ability to read minds because people are creeped out about it is now the only one with a chance to resolve a mystery that threatens pretty much everyone. It's a chance for redemption for her. It's her chance to prove that her ability isn't a bad thing to people that aren't herself. And if anything, is also a way to potentially prove that to her sister, who closed her third eye and shut off her emotions because of the hatred that she received from the people who hated them. Satori was literally the only one capable of figuring this out and solving this mystery in a timely manner that kept people safe. But between being demoted to extra and the pacing and padding being so awful, that I can't really see happening anymore. And now that she's become a victim in her own story, I don't think it's realistically possible for that opportunity to come again at this point. It took what could have been a really good premise, a really good mystery with a really good redemption for a character in universe was hated by everyone, potentially giving her the chance to finally be loved by people for the very reason that they hated her, and it fucking threw it in a garbage can and set that garbage can on fire.
So, yeah, all in all? I'm super disappointed by this series.