It is actually a release kit. L5R does not currently do prerelease, although they are planning to in the future.
There is a new learn to play set coming out this summer and from the L5R website there is going to be some really good cards in the decks.
(Traveling Peddler, Expendable Resources, Famous Bazaar, Chugo Seido, Final Duty, Kami Unleashed, Sneak Attack, Low Stance, Unpredictable Strategy, Laying in Wait, Will, Justly Earned Victory...) All cards that most decks can use and were hard to come by.
http://www.l5r.com/news/battle-of-kyuden-tonbo/