It seems like Sega Japan will be revealing a new title very soon. To be more precise they will be announcing the game or whatever it is that they are planning on the 12th of February. This was made evident by the new teaser site they have launched.
The teaser site is fairly simple. The date 2.12 pops up with various images appearing behind the date like a slideshow. Nothing too flashy.
Judging by the images; I would say that they are going to announce some sort of fantasy RPG/adventure game on the February 12th. However, that is pure speculation on my part as Sega Japan has not commented on this development and the information out there regarding what this site may be about is literally non-existent.
I guess we will find out more on the 12th of February like everybody else.