Layton has encountered six suspects along the way. Who are they? Also this is the metapuzzle, so it will use all of the puzzle answers.
Layton noticed that each suspect shared a similar trait, which helped clue him in on how to find the right room.
Despite how it seems, this puzzle is based on a game that has nothing to do with Professor Layton. Once you determine that other game, think about why there are exactly nine puzzles.