Katrielle "Kat" Layton is the protagonist of the Professor Layton game Layton's Mystery Journey: Katrielle and the Millionaires' Conspiracy. She is the daughter of Professor Hershel Layton.
Katrielle is described as being a funny person, who has an active imagination in solving puzzles and cases. She relies largely on her "miraculous instinct" to solve mysteries and jokingly mocks investigators that rely solely on concrete evidence. This causes some like Sherl to credit Kat's success to dumb luck. She'll often give imaginative or complex explanations for mysteries. This all leads some, such as Emiliana Perfetti, to not take her seriously as a detective.
Kat also has a healthy appetite, being able to put away a large dinner and still have room for dessert, not unlike Luke Triton.
Pre-game (Case 10)
Prior to the main events of the Millionaires' Conspiracy, Katrielle had stopped by Scotland Yard one day, presumably to get an update on the investigation of her father's disappearance. There, she met Inspector Ercule Hastings, who, at the time, was interrogating Ernest under suspicion of stealing research papers belonging to Gressenheller University professor Dr. Gene Ohm. Disgusted by Hastings's jumping to conclusions and lack of evidence, Kat convinced him to release Ernest and resume the investigation.
Gressenheller being her next stop anyway, Katrielle joined Ernest in returning to the university, offering to prove his innocence -or guilt- "en passant." Once there, her instincts lead her to retrace Ernest's steps that day to the letter, including stopping to smell roses. This lead to the truth of the case, clearing her friend's name.
In appreciation and affection for Katrielle, Ernest joined her as an unpaid assistant when she opened the Layton Detective Agency soon afterwards. The agency's slogan, "Any mystery solved," lead an amnesiac Sherl to test Kat's mettle with a puzzle before enlisting her services in uncovering his past. Kat, however, put this on hold in favor for a "more interesting" case- the apparent theft of the hour hand of one face of Big Ben, brought to her attention by Inspector Hastings.
- She is 21 years old.
- Katrielle is a name that means "God is my Crown". It is Hebrew in origin, much like that of her father. It is regularly spelled Katriel, or Catriel.