In that instant, when Takeo met Tanjiro's unfocused gaze, a chill ran down his spine.
But he quickly realized something.
Tanjiro wasn't looking at him at all.
His eyes were fixed somewhere behind him.
[ Behind me…? Is he looking at Mr. Hiru and the others? ]
Before Takeo could think any further, the weight at his waist suddenly vanished. Tanjiro had already snatched his nichirin and dashed straight toward the battlefield behind them.
For a brief moment, Takeo felt relieved.
But that relief quickly turned into panic.
"Wait! Brother! Sunrise is almost here!"
Without thinking, he ran after him. But he only managed to grab a torn corner of Tanjiro's haori before Rengoku pulled him back.
"Watch out!"
"But Mr. Rengoku! My brother—"
"I know! Stay here," Rengoku said as he twisted his body and rushed after Tanjiro toward the battlefield. "I'll bring him back."
The two sprinted forward in quick succession, heading straight toward the increasingly fierce clash between Hiru and Akaza.
Rengoku saw Tanjiro fling away the scabbard and charge directly into the middle of the two demons' fight.
In an instant, the blade in Tanjiro's hand burst into crimson flames.
The next moment, he brought it down in a vicious slash aimed at Hiru.
Even Akaza—who had been watching Tanjiro carefully—froze for a split second in confusion.
Hiru cursed under his breath and ducked low to avoid the strike.
"I can handle this! Kyojuro, get back!"
But Rengoku ignored him completely.
Without slowing for even a moment, he rushed forward. With a sweep of his blade, he deflected the shockwave from Akaza's incoming punch, then immediately reached out and hooked an arm around Tanjiro's neck, trying to choke him unconscious and drag him away.
But Tanjiro had no intention of leaving like that.
He stepped back and slammed the back of his head straight into Rengoku's nose.
Pain exploded through him. In the instant his grip loosened, Tanjiro crouched low, slipped free, and lunged toward Hiru once again.
Seeing him charge forward with his blade drawn, Hiru felt both relieved and exasperated.
Relieved that Tanjiro still remembered his hostility toward demons.
Exasperated that he had chosen him as the main target.
As Tanjiro rushed straight at him, Hiru's expression darkened slightly.
But instead of blocking head-on, he tilted his head just enough for the strike—aimed at his cervical spine—to slide into the gap between his collarbone and shoulder.
Then he tensed his muscles.
His right hand shot up, seizing Tanjiro's wrist and twisting it violently until the joint snapped, forcing the blade from his grip.
A moment later, Hiru kicked him away, sending him flying.
Akaza naturally wouldn't miss such a perfect opening.
He lunged forward at once, aiming to grab the sword embedded in Hiru's shoulder and tear the wound open even further.
But Hiru had no intention of letting that happen.
The instant he kicked Tanjiro away, he twisted his body as well, yanked the blade out himself, and hurled it far into the distance.
At the same time, he raised his voice.
"Get that kid into the shadows! He won't die unless his head's cut off! Sunlight's the real problem!"
"I'll going!"
Rengoku immediately turned and attacked Tanjiro again.
But an unexpected scene unfolded.
It was as if Tanjiro could foresee every strike.
Each time Rengoku aimed for his limbs, Tanjiro evaded at precisely the right moment.
Even though their speeds were nearly identical, neither could gain the upper hand.
When Hiru realized that Rengoku had understood he couldn't subdue Tanjiro quickly—and had instead begun steering the battlefield, just as Akaza had been doing earlier—he finally relaxed a little.
Still playing along with Akaza's plan, he also found himself wondering where Akaza intended to have Nakime open the door.
[ If he entered the Infinity Castle… ]
[ Would he have the chance to drag one more enemy down with him before dying? ]
But Akaza's tense expression revealed nothing.
No matter what Hiru said during the brief openings in their fight, Akaza ignored him completely.
At this point, Hiru could only conclude that Doma must have annoyed him badly enough for the young demon to develop selective deafness.
Just as that thought crossed his mind—Akaza's attacks suddenly intensified.
The force of the blow sent Hiru flying.
While suspended in midair, he finally heard it.
The unmistakable sound of a paper sliding door opening.
It was so clear that he instinctively lowered his gaze.
The ground below had vanished.
In its place yawned a massive opening, revealed by a sliding paper door.
Looking down through it, he saw rooms of every color stacked and tangled together in impossible layers, forming a chaotic city of dazzling lights.
Even a single glance was enough to make one dizzy.
Hiru was still airborne.
There was nothing he could use to steady himself.
If he kept falling, he would inevitably plunge straight into the enormous opening beneath him and Akaza—nearly ten meters wide.
He turned his gaze toward Akaza and smiled with genuine admiration.
"You really are capable…"
Akaza couldn't understand why Hiru would smile at a moment like this.
Yet the smile on Hiru's face suddenly shifted into stunned surprise.
[ What? What is he planning now? ]
Before Akaza could figure it out, someone suddenly stomped heavily onto his back.
Another step landed on his head as the intruder used him as a springboard to leap away.
The unexpected force knocked Akaza off balance, sending him falling downward.
Rage and shock surged through him at once.
Rage—because someone had dared to attack him from behind.
Shock—because his Blood Demon Art had never sensed anyone approaching.
As he fell toward the opening, Akaza twisted his body and looked upward, trying to see who had slipped past his perception.
But when he finally saw the figure that had used him as a stepping stone to leap toward Hiru—
His expression became almost identical to Hiru's.
Except his was filled with disbelief.
[ When did this brat—?! ]
Meanwhile, Hiru watched Tanjiro plant a foot on Akaza and launch himself stubbornly toward him.
Tanjiro grabbed Hiru by the throat and crashed into him, knocking both of them clear of the opening and onto the ground beside it.
Hiru was still momentarily stunned by the sudden turn of events.
But Tanjiro showed no hesitation.
Crimson flames flared to life.
In an instant, both of them were engulfed in fire.
A fierce burning pain spread through Hiru's body.
Yet he made no attempt to suppress the flames.
Instead, he seized Tanjiro by the neck and slammed him hard into the ground.
Then he immediately prepared to rush back toward the opening of the Infinity Castle.
There was no way he would let such a perfect opportunity slip away.
At the very least, he needed to leave some kind of mark inside the Infinity Castle.
But when he reached the edge of the doorway and finally saw the interior clearly, Hiru froze.
The dark side of the castle was covered in intersecting sword scars.
Many of the rooms had been completely torn apart by the slashes.
It stood in stark contrast to the bright, dazzling lights above.
[ Those sword marks… ]
[ Did my brother find the Infinity Castle? ]
But the hesitation lasted only an instant.
The massive door suddenly slammed shut.
At the final moment, Hiru managed to slash open his palm, letting his blood splatter across the paper door just before it closed.
Then he could only watch—
As the doorway vanished into thin air right before his eyes.