There are actually 3 online games from KRU but the one I've played, probably for almost 8-9 years is NexusTK (
http://www.nexustk.com/) It's not uber graphics game but there is plenty of strategizing and a strong online community with it's own justice system, clan system and even specialization for the 4 class of players they have (Poets, Mage, Rogue and Warrior). I'm the type of person who plays this stuff online in the winter, when I tend to hibernate more and then in the spring I suspend my account. I've pretty much done mages since I've started there; it's what I do best - my main character is an almost il-san Geomancer (subpath of the mages).
Just curious.
It is $10/month to play but the online community is excellent. The new owners of the game have added many new features and events to break up the routine of the game. Right now they are doing double experience bonus because I personally believe they'll be expanding the system yet again.