The game will take place in the fantasy world of "Labyrinth City" where the puzzle-solving archaeologist and the hot-blooded defense lawyer will work to unravel mysteries and protect the wrongly accused (although, not necessarily together).
The game will be divided into two parts: The Adventure Part and the Trial Part. In the Adventure Part, the player will control Professor Layton and solve puzzles around the city while gathering clues. In the Trial Part, Phoenix Wright takes the main stage in a special courtroom called a 魔女裁判 (Majyo Saiban translation: "Witch Trial") where multiple witnesses take the stand simultaneously. As the story moves along, the player will switch between the Adventure and Trial parts.
For the Tokyo Game Show next week, Level 5 has announced that they will have a playable demo available and Capcom has announced a special stage event on Sunday.
Professor Layton vs. Ace Attorney is scheduled for release in Japan on November 29th. No word on a western release yet.