When starting the game with all the pages, the game's music should play in rewind, this would allow you to perform an action in the world you otherwise wouldn't've been able to. This action is what allows you to collect the 6th body.
although we didn't get to implement a stronger connection to lore, we wanted to have it so that the weeping girl was the protagonist's friend (denoted by the "朋友" decal near her character). Upon learning that you need 6 bodies (after collecing the pages), the idea was that you now have a reason to kill even your friend. We never actually had the time to show this more clearly, as we wanted to finish the entire game within a week, and we also haven't playtested this, but I hope this ending still works!