Compile Heart’s recently launched NPG countdown still has twenty days left on the timer, but the secret may have already been revealed much ahead of time.
Found within the flash teaser site’s source code is the URL: http://www.compileheart.com/neptune_mk2/. This is where the current countdown site will lead after the timer hits zero. It’s not live, currently, but it should be by the next twenty days.
And of course, the main subject of the link: the “neptune_mk2” directory. This probably stands for Neptune Mark 2, or something along those lines.
Sounds like a Hyperdimension Neptunia sequel to me.