Kenshi looked at Shinobu's face, a small bead of sweat trickling down his cheek. 'I still didn't acquire the Transparent World skill,' he thought, memories of his training in the Mindscape flashing through his mind.  

Despite pushing himself to the limits, dedicating every hour to mastering the technique, he had failed to attain the ability to perceive the world with clarity and see through the people and demons. His reflexes had skyrocketed to near-Hashira levels, but the skill remained out of reach.

'Why?' Kenshi didn't understand. He had met all the requirements, endured the system's grueling simulations, and honed his senses to a razor's edge. Yet, he still did not know the final key to unlocking the Transparent World.

A sense of unease gnawed at his gut. He knew he was stronger than before, perhaps even surpassing Shinobu in certain areas, but her advantage lay primarily in speed and agility. Against an opponent as skilled and experienced as the Insect Hashira, mere strength might not be enough.

"Kenshi," Shinobu's voice snapped him out of his daze. "I can sense you've grown stronger, somehow. If I had known a little competition would motivate you to train so diligently, I would have used such tactics long ago." Her eyes fell on the bruises and scrapes marring Kenshi's hands, evidence of his relentless practice. "But it seems you may have pushed yourself too far, causing harm to your body."

Kenshi couldn't help but grin, despite the uncertainty within him. "Heh, even if I manage to beat you today, I'm still willing to take lessons from you." His gaze met hers, burning with determination. "But don't think I'll go easy on you."

Shinobu's lips curved into a slight, almost menacing smile as she unsheathed her katana, the blade gleaming in the fading sunlight. "You really think you're going to win, hmm? Well, I don't want to hear any more boasting. Let's just end this battle." Her tone remained light, but there was an edge of steel beneath the words. "The rules are simple: if you can place your sword against my neck, I lose. The same applies to you."

Nodding, Kenshi drew his own blade, the familiar weight of the hilt grounding him. 'Well, I have to win this somehow,' he thought, settling into a ready stance.

A hush fell over the gathered spectators - Tanjiro, Zenitsu, Inosuke, and the others - as a sense of anticipation thrummed through the air.

Swoosh!

The sound was little more than a whisper on the wind, but in that instant, a figure materialized before Kenshi, a blade sweeping towards his exposed neck with blinding speed.

To the onlookers, Shinobu's movement was imperceptible, her form blurring into a ghostly afterimage. Only Kenshi, with his heightened senses, and Mitsuri, thanks to her status as a Hashira, could track the Insect Pillar's lightning-fast strike.

Uhh!

Shinobu grunted, her katana halting mere inches from Kenshi's neck, intercepted by the cross-guard of his own sword. He had reacted with the barest fraction of a second to spare, his blade whipping up to deflect the blow.

Without wasting a moment, Kenshi disengaged, leaping back to create distance as he gulped in a steadying breath. 'Damn, she's going full-throttle from the start!'

Before he could formulate another thought, his instincts screamed a warning. He twisted, his sword arcing up to parry a thrust aimed at his back, Shinobu's form materializing behind him in a blur of motion.

The duel had just begun, and Kenshi found himself immediately overwhelmed, his blade moving quickly as he desperately deflected and evaded Shinobu's unrelenting onslaught.

Her sword was an extension of her body, the strikes appearing from every conceivable angle in dizzying combinations and feints. Each time Kenshi thought he had read her movements, she would pivot with blinding speed, her blade slipping past his defenses to leave a hair's breadth from severing flesh.

'She's not even using Insect Breathing yet,' Kenshi realized with a spike of dread, his arms trembling from the strain of matching her blinding speed. At this rate, he wouldn't last much longer.

Gritting his teeth, Kenshi asked the system to activate the Demon Slayer Mark.

[Demon Slayer Mark Activated. The Skill Will Shut Down After 5 Minutes.]

[5:00]

[4:59]

Kenshi felt his demon slayer mark flare to life, the intricate pattern burning across his abdomen like searing brands. He had already tested it in the Mindspace, so he knew full well how to balance his power.

In an instant, his strength increased, his movements became even more fluid and responsive.

When Shinobu's blade lashed out in a series of thrusts, Kenshi twisted between each strike with grace, his sword weaving an impenetrable form of parries. For a few fleeting moments, the exchange became even, Shinobu's eyes widening as Kenshi met her onslaught head-on.

'How did his speed and strength suddenly increase so much? Was he hiding his strength to catch me off guard?' Shinobu thought as shock flickered across her features, quickly replaced by a look of intense focus. She would not be caught off-guard again.

Kenshi could feel the demon slayer mark thrumming through his veins, heightening his already formidable abilities to their utmost limit. But even this advantage could only carry him so far against Shinobu's sheer skill and experience.

The Insect Hashira's eyes narrowed, her muscles tensing as she focused. Kenshi's finely-honed instincts detected the shift, recognizing that she was going to use her breathing technique.

"Insect Breathing, Fourth Form..."

Shinobu's form blurred into pure, incomprehensible speed, her blade leaving afterimages in its wake as she launched a blindingly intricate flurry of slashes that seemed to emanate from every direction at once.

Gritting his teeth, Kenshi poured every ounce of his focus into reacting, his mark-enhanced body straining to keep pace. Sparks flew as their blades clashed again and again, the sheer ferocity of Shinobu's assault gradually overwhelming his defenses.

A shallow cut opened along his cheek, followed swiftly by another scoring his shoulder. Kenshi grunted, his movements becoming increasingly desperate as Shinobu's relentless storm of steel drove him back, step by step.

The world around them had ceased to exist, replaced by the flashing blades and ringing steel. To the spectators watching with bated breath, the combatants appeared as little more than blurs of motion, trading strikes too quickly for the naked eye to follow.  

Only Mitsuri, her keen senses heightened by experience, could discern the ebb and flow of their lethal exchange. A look of respect glinted in her eyes as she watched Kenshi match Shinobu's blade for blade, but there was also concern etched into her features.

She could see he was being gradually overwhelmed. Somehow, he seemed to be weakened. That's right; his demon slayer mark's time was almost coming to an end. Once it faded, there would be nothing to stop Shinobu's victory.

Seeing there was less time left, Kenshi's movements became wilder, more frantic in those final seconds. He launched himself into a spinning wheel-kick, his blade sweeping in a horizontal arc towards Shinobu's midsection in a feint.  

When she moved to counter, he dropped into a slide, his sword lashing out towards her ankles with blistering speed. But Shinobu was already gone, her body blurring with quickness as her katana flicked out, poised to end the duel with a strike at Kenshi's throat.

Time seemed to slow to a crawl in that instant. Kenshi could feel the demon slayer mark fading away as the system announced the time was over, his strength waning. He watched Shinobu's blade carving through the air towards his exposed neck, knowing there was no way to stop or evade the strike in time with his sword, as he didn't have enough speed.

'Hah, despite all the training, all efforts to grow stronger, I had still fallen short. Perhaps I indeed became overconfident after the system awakening,' he thought in his mind as he was about to give up.

But in that moment, something shifted within Kenshi's perception, like a veil being lifted from his senses. 

Suddenly, the world around him crystallized with clarity. He could see everything - the minuscule flexing of Shinobu's muscle fibers, the subtle shifts in her center of gravity, even the flow of blood pulsing beneath her skin.

It was as if time itself had slowed to a crawl, each fractional movement rendered in exquisite detail before his widening eyes.

The Transparent World.

He had finally awakened the ability, his senses operating on a level far beyond normal human or a normal demon slayer's perception. Kenshi could track the path of Shinobu's blade with perfect, unhurried clarity, his gaze penetrating the flurry of steel to discern the flow of force and momentum behind it.

More than that, he could perceive the muscular contractions presaging her every movement, giving him a window into her thought processes, into the combat calculations unfolding within her mind.

Shinobu's eyes flashed with surprise as Kenshi's body blurred into motion, his form bending and twisting around her strike in a manner she had never witnessed before. It was as if he knew the trajectory of her sword even before she swung it, his evasion occurring before she had even fully committed to the strike.

A smile appeared on Shinobu's face, as though she was enjoying the battle, but only Kenshi and Kanao, who knew her every smile, and Tanjiro, who could smell emotions, knew that she was becoming angry.

Shinobu's blade once more found only empty space where Kenshi's body should have been. He flowed around her like whirling steel like water around a rock, his own counterattacks forcing her onto the defensive for the first time since their duel began.

'Impossible!' Her mind raced as she parried and deflected a blinding series of thrusts and slashes, each blow seemingly aimed with uncanny accuracy. 'How is he anticipating me so completely?'

To the spectators, it appeared as if their battle had transformed into a dizzying display of light and shadow. Streaks of luminescent steel clashed and wove around each other in a hypnotic, almost dreamlike cadence.

But for Kenshi, everything had become clear. He could see the pathways of force behind each of Shinobu's strikes, her physical prowess laid bare before his eyes.

When she attempted to bind his blade in an intricate shell-guard and disarm him, he flowed around the maneuver with grace, his own sword lashing out to target the precise areas where her balance was most compromised.

Shinobu's breathing grew labored, her brow furrowing in concentration as her attacks grew increasingly erratic, desperately trying to regain some semblance of control over their deadly exchange.

But no matter what technique or feint she employed, Kenshi seemed to anticipate it before she had even finished formulating the thought, his body and blade always one step ahead.

'This level of perception...is beyond anything I've ever encountered,' Shinobu realized, a bead of sweat trickling down her brow as their duel raged unabated.

Just then, a thin sheen of gleaming liquid began to coat Shinobu's blade as she slashed and wove between Kenshi's counters. With each exchanged strike, she left behind glistening trails of viscous liquid that smelled wonderful, lacing the air between them with a miasma.

Shinobu saw a panicked expression on Kenshi's face.

'Haha, he was putting on that stoic face from the moment he started fighting back. It's good to see him panic a little.' Just as she was preparing her next move, Kenshi's form suddenly blurred as it disappeared.

Shinobu's instincts screamed as she suddenly turned around to block an attack that she sensed.

However, she felt the cold edge of a blade resting on her neck as Kenshi stood behind her with the same stoic face.

"Teacher, I think I won the battle," Kenshi said.

-------------------

Author's Note - IRL problems caused this novel to stop, but now everything is good, regular chapters will be uploaded. 

Daily chapters - 1 

Time - 10:30 EST

World count - 1800 to 2000 worlds.