[spoiler]Can somebody explain Sumi route ending of Monobeno?

[Mikimir]

I recently finished Sumi route in Monobeno and man that game is hard to understand. The dialect made it even worse too, though not by a lot. Spme of my questions are:

Natsuha turns out to a an embodiment of something. What exactly is it? I know that Himemiya explained what it is but I couldn't really understand how it works.

Okay so the spider youkai (forgot her name) prohibits the protagonist from meeting Natsuha. Was it because he wasn't able to found out what was happening to her fast enough?

I thinks that's all for the questions I have. God I suck at Japanese I should stick with VNs like Natsuiro Recipe

Edit: another question; I think I'm asking this just because I don't remember but what caused the world of youkais and the human world to collide? I took a break from going any further into her route few weeks ago (my brain couldn't take it anymore) so I don't remember what exactly happened

[rainsismyfav]

Now that I think about it.. I forgot the details myself. Oh geez......

 

It'd help me too if someone answers you.

I vaguely remember Natsuha having seen something that she shouldn't have seen (???) around the waterfall area.