SegaEmu is holding a Sonic Festival during April to celebrate the debut of the Mega-CD version of Sonic CD on the service. As part of the festival, users of the Japanese-only service will be able to play Sonic 2, Sonic 3, Sonic & Knuckles and Sonic Eraser for free in exchange for downloading selected titles.

^ Sonic Festival logo
Sonic is appearing in the Puyo Puyo Carnival to promote the release of Sonic Riders. Held to commemorate the 15th Anniversary of the Puyo series, the carnival allows Japanese players to engage in online battles of Puyo Fever at no charge.

The strangest promotion has been saved for last. The website of Japanese restaurant Yumeshiya shows a picture of Naka serving food.
It isn’t exactly clear what Sega would gain from holding a promotion with a restaurant such as Yumeshiya, which doesn’t appear to be a particularly famous or popular franchise. The text that accompanies the image is in JPG format making it inaccessible to machine translators.
The website is referenced on the Sonic Channel Staff Column together with an enigmatic headline that reads “A serious announcementâ€￾. Visitors to the site have taken this as indicating that Naka has left Sonic Team. However, it is important to remember that the Staff Column regularly indulges in Sonic related pranks and so the photograph is likely to be part of April Fools joke.
http://www.yumeshiya.com/yumeshiya_naka2.jpg