I'm a librarian who loves anime, manga, and reading a wide variety of genres.
"Challenge to the reader: The clues are all there. Can you solve this case?"
Shimada did this exact same thing in The Tokyo Zodiac Murders. It was just as aggravating then. I did end up reading Tigus's hints, and I'm still stumped. My current theory is something something,
(show spoiler)::siiigh::
I have to go to work in a bit, so I get the whole workday to think about this, and then I'll finish the book up and find out the truth.