Is this the sort of thing you are looking for? http://tinyurl.com/4e76t9 There are four different fullsize Nikkei futures contracts on three different exchanges in three different countries, plus an eMini Nikkei contract. I assumed (guessed) you were talking about the one with the largest volume and open interest.
Don't forget the two SGX ones. Mod, do a search for nikkei or n225. There is lots of discussion here.