(Spoilers for Meakashi) I find it interesting how Ryukishi constructed the mystery of this chapter. There’s no outright contradiction with having Mion be the culprit, at least up until the final encounter where Mion was already dead. Every single piece of the puzzle seems to fit just fine with Mion as the culprit, right down to Shion’s insanity at the end. But then you hit that final encounter which is simply contradictory. Of course the contradiction is revealed at the same time some other curious points are so it’s easy to just stop thinking right there because there’s too much you don’t get. But if you do continue thinking and conclude it must be Shion who went there, …well actually even then there are a ton of apparent inconsistencies that make finding the actual truth extremely difficult, such as Shion and Mion referring to each other by their original names. There are hints, but it’s shrouded in darkness all over.
I’m actually curious to see if people manage to solve it before Meakashi hits.