From the announcement:
It's been one year since the release of the free version of Kaigaku RPG. In honor of that event the premium version is now on sale for half off. If you're one of the nearly 2,000 players who've downloaded it, or of you're new to the game, now's the time to jump on board.
This version has a lot more content, including 18 more schools for your characters and a vastly expanded setting. Pick up Kaigaku today and start enjoying OSR-inspired samurai adventures today!