From Sega Retro
@barai was a label given to some Sega Dreamcast games in Japan, starting with Eternal Arcadia. Similar to demo discs, @barai games only allow the user to play through a small section of the game, typically the beginning, however unlike demo discs the full game can unlocked by purchasing it via the Dreamcast's online service. Stores charged for the @barai versions of games, though this price was far cheaper than ordinary Dreamcast games.
List of @barai Games