I have no idea if this is a spoiler (there's so many files and after several playthroughs, I don't know what is revealed vs what is already known from the beginning), but why was The Kusabi helping Sae wreck that village? Or were they both causing chaos independently and it just so happened that you needed to fend them both off?
It may be in a file somewhere but with over 100 files, I can't remember everything. The first time we see The Kusabi, he's with Sae in a way that would imply he's her heavy. So what is his motivation to follow her commands?
Also, is it actually Sae that turns evil or is her spirit corrupted by the abyss and it's more of a hellish echo of Sae that's causing all the problems? I feel like once Yae's spirit reentered the village, a regular Sae would have at least calmed down being reunited with her sister. Unless she's still mad at her for leaving