Letter from Kei 1 is a file in Fatal Frame III: The Tormented.
Sorry for not writing for so long. How are things with your fiancee? I'm continuing my investigation of the urban legend.
Like I thought, my niece's symptoms bear many similarities to the strange disease associated with the urban legend. I think most of the story is groundless rumor, but I've heard there was a psychiatric study done. If you have it, I'd like to see it. Maybe it will provide a clue.
I'm taking a break from all of my other work to devote myself to studying the urban legend. I'd like your help. According to the documents I've studied, that camera I sent you is apparently a rare "Camera Obscura".
Given where I found it, it may have some connection to the missing people and the urban legend. If you hear anything, please tell me.