Hey, if any of you can't beat this fight, I'll share a strategy that won me a
Flawless Victory on him.
First, I know your character is randomly picked for you, and this could take a while, but keep restarting the fight until you're given Dairou.
Once this is done, open the fight by sidestepping immediately, as he almost always comes out swinging. Instead of hitting him, take the one second you have to pull out your sword. This is the only stance you'll need.
From here on, you'll need to do only two things. One is rely on a fast and powerful combo that for some reason he almost never blocks the last hit of, allowing you to knock him down fast and hard. It's 1, 1, FORWARD + 3.
The AI almost always allows the final hit to ream him, putting him down. Once he's on the ground, rush in fast and as he gets up, once again sidestep IMMEDIATELY, since nine out of ten times, he'll get up and start a combo on you. When he misses, use the 1, 1, FORWARD + 3 combo AGAIN.
Keep rushing in and sidestepping him as he gets up. Don't just swing, cuz he'll duck it and punish you. Stay aggressive and don't mess the combo up.
Seriously, this worked. I don't know anyone else that's gotten a Flawless on him.
BTW, if he blocks this combo entirely, just sidestep right away, don't even block, as he'll just throw you. Then try it again.