In a press release yesterday (translated by Andriasang), Level-5 announced that the Professor Layton series has shipped 12 million copies worldwide.
The first game, Professor Layton and the Curious Village, has also passed 1 million copies shipped in Japan. This marks one of the company’s internal milestones, as the game reached that mark worldwide at the end of April.
The newest title, Professor Layton and the Mask of Miracle for 3DS, has already been released in Japan, while a U.S. release remains undetermined.

