I have just thought about Dariou's story line and I have come up with this idea. This thread was inspired by an earlier thread posted on Dariou.
I think that Dariou is a ronin. A ronin is a samurai without a master. I heard that Dariou want's revenge on the killer of his master. What better way to make a rival for Kenshi?
Kenshi's story has him travel with Sub-Zero in Outworld. In his story it says that he feels someone watching him in the shadows. That someone would be Dariou who wants revenge on his master's killer.
How would Kenshi kill Dariou's master? Well, Kenshi was a wandering warrior who challenged the greatest sword fighters through all of Japan. Kenshi fought Dariou's master and killed him battle. Dariou must have been enraged and he trained upon the day when he would meet Kenshi. Dariou could be an evil ronin warrior from the Netherealm and he could team up with Onaga for the chance to meet Kenshi in combat.
This could be a Sub-Zero and Scorpion type of rivalry and it would end in bloodshed. What do you think?