Square Enix has launched a mystery teaser site for an as yet unnamed title. There's talk already circulating that it could be a sequel to The World Ends With You, a project that has long been hinted at by Tetsuya Nomura (according to the report on andriasang).
You can check out the site right here. Alternatively, you can wait until the timer runs out (see the picture below), then we'll report back our findings.