In D&D 3.0 there was the Oriental Adventures release that was a d20 version of Legend of the Five Rings (L5R), which is heavily based on feudal Japan in a high fantasy setting. In that one they simply added a skill called "Iaijutsu Focus" and new uses for Sense Motive to read your opponent.
[Iaijutsu Focus] Check: (OA pg58-59)
If you attack a flat-footed opponent immediately after drawing a melee weapon, you can deal extra damage, based on the result of an Iaijutsu Focus check. In addition, if you and your opponent both agree to participate in a formal iaijutsu duel, your Iaijutsu Focus check replaces your initiative check for the ensuing combat.
In an iaijutsu duel, you and your opponent make opposed Iaijutsu Focus checks, and the winner accumulates extra damage dice according to the accompanying table.
You can also use Iaijutsu Focus in preparation for striking an inanimate object, assuming no distractions. Your extra damage is halved, just like your ordinary damage. This is the technique martial artists use to shatter objects
Starting at a roll of 10 you get +1d6 to your damage with a successful Iaijutsu roll, with +1d6 for every 5 you score higher is another +1d6 (max +9d6 at 50 or higher). There are feats and classes (Most notably the Iaijutsu Master prestige class on pg41) that compound on these rolls if you want to specialize. Although the Samurai basic class from OA was rather disappointing to me as it seemed to try and blend fighters and anointed knights (Book of Exalted Deeds).
Sense Motive checks had the added functionality of letting you know a character's level (DC 15), Iaijutsu SR (DC 20), and full attack bonus/damage with primary weapon (DC 25), and is the first step of an actual Iaijutsu Duel in this system.
Next comes comparing the skill rolls as the "focus" phase, and then the "strike" phase:
Iaijutsu Duel [Strike Phase] pg 82
The first round of an iaijutsu duel’s strike phase is essentially a surprise round: Each combatant can take only a partial action (usually a single attack) in addition to drawing the weapon (a freeaction, assuming each duelist has the Quick Draw feat). With a successful hit, a duelist deals the bonus damage achieved through his Iaijutsu Focus check in addition to normal (or critical) weapon damage. The initiative winner strikes first, naturally. The initiative loser, if he survives, must attack on his action as well—he cannot hold back the ki he has focused. Note that since the loser is not attacking a flat-footed foe, he does not get the opportunity to strike with his bonus damage dice from Iaijutsu Focus.
If the initiative check is a tie, the attacks actually occur simultaneously, with both samurai considered to be flat-footed. On rare occasions, two samurai have been known to strike each other down in the same instant in what is called a karmic strike. After the initial round of the duel, the two samurai can continue fighting in normal combat, if both survive. They no longer receive any bonus damage dice to their attack rolls unless the circumstances under which Iaijutsu Focus checks may be attempted somehow arise again in the course of the fight (the combat ends and one or the other returns his weapon to its sheath)
There is a Samurai base class in Pathfinder, although it seems to be more of a tank than what you're looking for. Truthfully, if you want to have something based around counterattacks, your best bet is to work around Attacks of Opportunity but otherwise there don't seem to be many features built into PF that I know of for more fluid movement beyond "you get +X to AC/To Hit/Damage if trigger met". Once again tagging to OA, there's a feat called "Karmic Strike (pg63)" that while in effect gives you a -4AC and if an opponent hits with melee you get an AoO against them.
Ultimately as a personal note, I don't feel that d20 truly captures a give and take system even if I try to factor in Swashbuckling Adventures source material that tried to port 7th Sea materials into the game. With those there were more defined rules for counters (IE riposting) which helps add some customization but still doesn't quite do justice if you're familiar with the source materials. Even though L5R still uses a one turn/round structure but the rolling mechanic, and (seemingly FASA inspired) turn structure allows for a lot less convoluted turn where a D&D turn can explode rather quickly into several parts attempting to be contained in exactly one moment.