Or Monthly Forked Tree Cup? Tsuno is testing the servers capabilities by running a free tournament on tenhou at 22:00 JST or 13:00 GMT. 1st-10th get 30 days of premium membership. Last time Tsuno tried running a free tournament ([Saki Cup])) it crashed the server.

Tsuki Matagi Hai
Date:  30/11/2010 22:00 – 2:00 JST
Rule: Tonpuu ariari
Prize: 1st-10th 30 days of premium
Enterance fee: free
Ranking: Best score from 3 consective games
http://tenhou.net/0/?90349028