Well, don't worry. It removes purple fog from pages you haven't gone to yet. It's a feature without function. And since that's the only thing the purple lense does, it basically just means you have to press one extra button during a chapter. Doesn't add anything to the gameplay. Doesn't add anything to the story. I'm pretty content to pretend it doesn't exist except that it makes me think about cool stuff they COULD have done.
So yeah. The next three chapters are about a kid named Koji who thinks wearing a mask and playing hide and seek will help save his face. Spoiler warning, the woman in black is a pro seeker. He gets found, it's implied that she found him cause he was playing with me but I feel zero attachment or guilt, and then I have to dispel his evil spirit.
The game did something really cool in this final part of the "Koji trilogy". I had to tilt a page up to make object in a picture slide into position. Then blood dripped on a page and when I looked up a ghost was above me like the boy from Ju-on (love that movie). My only complaint here was the prompt for the tilt the page puzzle was phrased such that I thought I was supposed to either slide the book left or un-crumple the image with my hand. I imagine that issue falls on the localization team though, rather than the developer.
The woman in black is looking for someone specific and desires someone to stay with her. So I guess she's looking for the person who left her but is willing to take her grudge out on anyone who tries to leave her during that search.
The story is not bad, but I've seen this done better. Heck, I have a book that you investigate as you read that's sort of an ARG and it's more interactive than this video game thus far. I wanna like it, but I feel like I'm playing something put together as a cheap gimmick rather than a full game. But it was sold as a full game at the price of a full game.
Also, I got a darkness lens at the end of this section. Am I gonna get a new lens every three chapters that I only use once?
If the camera reacted to "locked" pages by showing the obstacles I can't pass without special lenses before I get the lenses (like a red door in Metroid), these lenses would feel like an achievement. But since pages only react when the game says it's time, the lenses serve absolutely zero purpose at this point.