Layton's Mystery Journey

Layton's Mystery Journey: Katrielle and the Millionaires' Conspiracy
North American Nintendo 3DS cover art
Developer(s)Level-5
Publisher(s)Level-5
Director(s)Akihiro Hino
Designer(s)
  • Kuniaki Iwanami
  • Satoru Nagayama
Programmer(s)Takashi Azuma
Artist(s)
  • Takuzō Nagano
  • Masako Arakawa
Writer(s)Akihiro Hino
Composer(s)Tomohito Nishiura
SeriesProfessor Layton
Platform(s)Android, iOS, Nintendo 3DS, Nintendo Switch
ReleaseiOS, Android
  • WW: July 20, 2017
Nintendo 3DS
  • JP: July 20, 2017
  • NA/EU: October 6, 2017
  • AU: October 7, 2017
Nintendo Switch
  • JP: August 9, 2018
  • WW: November 8, 2019
Genre(s)Puzzle, adventure
Mode(s)Single-player

Layton's Mystery Journey: Katrielle and the Millionaires' Conspiracy is a 2017 puzzle video game by Level-5. The seventh main entry in the Professor Layton series, it was released for Android, iOS, and the Nintendo 3DS, in 2017, and an enhanced port for the Nintendo Switch in Japan in 2018, and worldwide in 2019. The game centers on Katrielle "Kat" Layton, the daughter of famous archaeologist and puzzle-solver Professor Hershel Layton. With the help of her assistant Ernest Greeves, she solves cases in and around London, alongside a talking dog that, for reasons unknown, only the two of them can understand.

Unlike prior Layton games, Mystery Journey has no definitive overarching narrative, with most of its main narrative's premises existing as a basis for a set-up, ending in a cliffhanger leading into the 50-episode anime series sequel Layton Mystery Tanteisha: Katori no Nazotoki File, which aired on Fuji TV from 2018 to 2019.

A manga adaptation of the game drawn by Hori Oritoka began serialization on March 20, 2018 in Shōgakukan's Ciao magazine.