With his initial counter being interrupted during its process, the swordsman had no time to fix a possible error or a mistake in his attack due to the close proximity between the two fighters. But to improvise somehow now that everything is in motion, there were a few ways that was available to him that he could use to parry, or at least lessen the amount of damage that he would receive to some extent.
Despite the motion and the humming of the blades cutting through the air, the quick unsheathe of Tenkai's Muramasa out of its saya was a more precise, and sharp, tone which the swordsman is familiar to due to the similarity with his own unsheathing, alerting him of a possible method of retaliation during his action. But too late to stop his right blade from looping back behind his head after the parry, and the swordsman placed in a posture that had his entire left side exposed to a possible counter...
*It's not over yet!*
The attack is still unfinished. His own move has yet to be interfered.
Eyeing Tenkai moving towards the swordsman's left to attack, the swordsman lashed out with his left blade, suddenly shifting his action into a diagonally upward slash by swinging his left arm out to his own left side - causing the left blade that was anchored to his right side to careen along with the motion. With Tenkai close enough to initiate a stab towards the swordsman's left abdomen, the swordsman used the force from his left blade to twist his torso accordingly to the shift of momentum, causing him to turn in a counter-clockwise rotation as Tenkai's stab neared its mark.
Shifting the trajectory path of his left slash, the objective was simple; Push the Muramasa away from his respective left from the slash, causing the stab to get diverted through the skidding and scraping sounds of his left blade - or his left bracer - in resistance against the Murasama blade. Some of the cloth on his left abdomen was ripped by the close proximity from Tenkai's blade, but with the swordsman turning to his own left - and the left blade coming to interfere, the stab at best came with a light cut across the swordsman's left side - drawing up a bit of blood, but nothing that would seriously affect his ability to fight.
KSSSHHK!
Knowing full well that Tenkai also had the scabbard held on his left, the swordsman has full intention in attacking with his right blade immediately once Tenkai was close enough, the right blade already cocked back behind the swordsman's right side of his head from the loop before. Somewhat mimicking the style of the use of a Chinese Dao before a strike... Keeping his left blade to his respective left after the arc and acting as a parrying device should the Monk have some tricks up his sleeves, with a short step-in with his right leg and an immediate, heavy downward swing from above, the swordsman would bring his right katana into a near downward slash towards Tenkai's right neck - as if wanting to cleave Tenkai into two halves from the right neck down to the left torso.
Knowing well that there was a good possibility of Tenkai dodging the blow or using the scabbard as defense, even a counter... unless there was the intent to seriously injure the monk, half-assed attacks would only spell trouble for the swordsman himself. And, having intentionally used the back of his blade for the attack instead of the sharp edge - should the attack actually hit... Well, at least it won't cut the monk in half. Probably give a rather nasty bruise and some blunt pain after the fight - optimistically.
But regardless if the blow would strike home or not, the swordsman would halt the force of his right blade if it missed in midswing, not wanting to go with the entire flow and open up his other side for an opening that the monk might exploit. It would also act as a means of deterrence, with his right blade held in front of the swordsman, pointed at Tenkai's general form as if like a Rapier in one possible outcome, covering up just a bit more of his own openings, and the left blade held at bay to thwart a possible use of the Murasama against him.
But only the results would tell - and the swordsman has to be careful in all of his motions against the Monk and his blade.
EDIT:: (Due to some slight misinterpretation of actions, here's an corrected version of the action.)
He stressed his motion back, already hearing some fleeting motion from his left side as he tried to react to the monk's clever counter.
Just as Tenkai went forward for a stabbing motion at the swordsman's abdomen, the swordsman would attempt to move his left arm downwards in a quick, clockwise arc hugging his torso, to protect his more vital spots from being attacked - a hastily erected defense. A bit slow in response though - since there was a slight pause during his recoil, the stab from Tenkai struck just for a split instant into the swordsman's position, puncturing the cloth and into a bit of flesh successfully.
But the draw of first blood ends there. With the swordsman moving his torso to the left along with the stab immediately after contact, and pushing the blade away to his own respective left due to his left arm coming down to push it away, the stab scraped along the left side of his abdomen, causing some blood to spill from the fresh slash wound, and the sudden grimace on the swordsman's face.
"Hrgh...!"
There was no doubt that the swordsman felt the all-too familiar sensation of his body acquiring a fresh wound. And despite knowing the sensation well from previous fights and previous experiences...he was never able to get accustomed to the sensation, each one feeling just as horrible as the last, if not worse.
Yet, despite suffering a successful strike from Tenkai, the positioning that both of them had partook was enough for the swordsman to continue on where he had left off; the Muramasa being pushed away to the best of the swordsman's respective left by the swordsman's left arm and intimacy, and Tenkai's left side pressing against his own, allowing for the swordsman's own countermeasure.
With his right blade held behind his head, the swordsman had his right hand swing upwards with a flick of the wrist, causing his right blade to whip out along the outside of the swordsman's own left shoulder, barely grazing himself.
And in Tenkai's perspective, this could be seen as a sudden flash of light glancing off of his right blade - Which would be heading right towards the Monk's general upper left body and face in such close range.
Not strong enough to slice through anything, since it was a flick - but it would certainly be more than enough to unnerve some people, and cut somewhat into exposed flesh if he was lucky.
Bonus points if the swordsman is able to get a successful strike on a more sensitive part of the body - like the side of the face, the shoulder, or just a slash wound to repel Tenkai from sticking so close to him.
In the meantime though - the swordsman would, if able to, try and create some distance between the two when he spots an opening, while using his left arm as a means to protect his left guard - not really liking the feeling of getting more wounds... But better than a slash wound on the torso, that's for sure.