Thanks for finishing it! For the umbrella/lantern youkais, the idea is that you can fairly easily move around their sight, and if not, then you can use Keine to temporarily "devour" them from history while you take care of surrounding threats.
I also understand that the last five levels aren't very difficult. While they were meant to be more story-focused and not as hard as the previous 5, I had to redo them because I had to cancel their actual main gimmicks, which was bunnies that the player had to block their view with events (Boulders, mostly) to move around them, and the "special NPC" using their powers to give you the object you needed to solve the room after some time.
But no matter what I did in the code, bunnies could always see through both walls and objects, which made them impossible to deal with as planned, so I scrapped them for a gimmick that I was hoping to keep for the post-jam levels: the rolling log. The special NPC only ended up being used in the final level because it took longer to setup the effects (including its 3D model) than I expected, and was just kind of mechanically lame in hindsight (not to mention even more taxing on the engine offline).
The last 5 levels I plan to add will be more focused on challenging the player, and will also finally involve rooms that are a tad bigger than normal too, so hopefully that will be more satisfying as a finale gameplay-wise.