Hiru looked at the railway tracks stretching endlessly ahead and couldn't help but sigh.
"Hey, Kitaro, do you think there's something wrong with my brain?"
"Gah?"
"I left several hours after the train departed, yet here I am running along the tracks trying to catch it. Even with good stamina, this is a complete waste, isn't it? And even if I somehow did catch up, it would only be at the final station anyway. So why didn't I just head straight to the terminal and wait for them there?"
Even as he said this, Hiru didn't slow down in the slightest.
"I must be low on sugar lately if I'm making decisions this stupid."
"…You've been running for almost three hours and you're only realizing that now? Gah?"
"It's because I never imagined something called a train could move this fast," Hiru said with another sigh. "An average person runs maybe one or two meters per second. Covering seven or eight kilometers in an hour would already be impressive. But that train? It must be going at least forty kilometers per hour!"
"Sure, it's convenient for people. A trip that used to take three or four days can now be finished in just a few hours. But moments like this make me hate technology! Even though I wasn't running at full speed, that train is still ridiculously fast! The world is changing way too quickly!"
Kitaro was about to reply when he suddenly flapped his wings and shot upward.
Hiru stopped, confused.
"Hey! Are you seriously just going to leave me here? That's a bit much, don't you think? I was only complaining a little! …Huh? What's that?"
With his excellent night vision, Hiru saw Kitaro intercept another Kasugai in midair. The crow had a cherry blossom ornament on its head.
Kitaro guided it down toward him.
Hiru raised his arm, letting the crow land.
"I remember you… you're Kyojuro's crow, right? Your name is… Kaname?"
"Yes, Hiru-sama! Please hurry and support Rengoku-san!" Kaname was panting, but his voice carried clear urgency. "The situation is extremely critical! We've encountered an Upper Moon!"
Hiru's expression immediately turned serious.
"Which Upper Moon? Any distinguishing features?"
"Yes! A demon with peach-colored hair and tattoos covering his entire body!"
"…Akaza."
Hiru fell silent for a brief moment.
"He's a martial artist who pursues combat above all else. He probably wouldn't try to kill Kyojuro immediately. How long did it take you to fly here?"
"I also stopped at other Wisteria Houses along the way to request reinforcements!" Kaname said anxiously. "It took quite a while! But the straight-line distance from here to the incident site should be around seventy kilometers!"
"Seventy kilometers…" Hiru slowly exhaled. "Alright. That's not too far. Continue notifying the nearby houses. I'll head there at full speed."
"Yes! I'm counting on you!"
After watching Kaname fly off again, Hiru stretched and loosened his joints.
Then he glanced sideways at Kitaro on his shoulder.
"Cutting straight across would make it easy to lose our bearings. I'll follow the tracks at full speed instead. Keep an eye out for junctions. Let's try to get there within an hour."
"Gah! If you sprint like that, will you still have the strength to fight afterward?"
"Don't worry," Hiru replied. "Right now, I'm basically a stamina monster."
"Got it, gah!"
Kitaro hopped into a specially sewn pouch attached to the weapon box.
"I'll point out the direction whenever we need it!"
"Thanks. I'm counting on you."
Hiru suddenly kicked off the ground.
His body shot forward like a shadow.
Where Kitaro couldn't see, faint signs of his demonic traits slowly began to emerge.
When he heard that Rengoku and the others had encountered an Upper Moon, Hiru had felt both shock and relief.
Thankfully, he had foolishly chosen to travel this way.
And thankfully—
The Upper Moon they had encountered was Akaza.
The memories Hiru had taken from Kokushibo allowed him to clearly understand what kind of demon Akaza was.
After Muzan turned him into a demon, Akaza behaved somewhat similarly to Kokushibo. He would only eat humans when he felt hunger.
In fact, in that regard, Akaza was even stricter than Kokushibo.
Kokushibo wandered the world in search of challengers to refine his swordsmanship, deciding whether to devour them depending on how hungry he felt afterward.
Akaza, on the other hand, would only seize someone to eat when he was starving to the point of nearly losing his sanity.
He never ate women.
He also never attacked women.
Of course, if a woman happened to be caught in the middle of a battle, he wouldn't go out of his way to save her either.
More than a hundred years ago, before one of the Upper Moon meetings, Kokushibo had once seen Akaza toss money—of unknown origin—to a flower-selling mother and daughter on the street.
Later, after the meeting ended, Doma ate that very mother and daughter.
Akaza challenged him to a Blood Battle.
Their already poor relationship only deteriorated further after that.
Kokushibo had once described Akaza with a single evaluation.
"Pure."
He was a demon with an extreme passion for martial arts.
It was precisely because of that quality that Kokushibo had spared Akaza when he once challenged him, instead of devouring him.
Hiru also remembered the time Yukinashi Aoba encountered Akaza.
Although Aoba had been critically injured, the wounds had accumulated gradually. Individually, none of them had been fatal blows to vital points.
Aoba himself had said that throughout the entire battle, Akaza kept trying to persuade him to become a demon—like a door-to-door salesman pushing a product.
It wasn't until Aoba attempted to exploit the situation and nearly succeeded in turning the tables that Akaza finally became truly enraged.
Taking all of that into account—
Hiru was eighty percent certain that Akaza would not immediately try to kill the straightforward Rengoku.
But there was always the chance that something could go wrong.
Hiru looked up at the moon tilting westward and began calculating the timeline.
The train had departed at six in the evening.
He himself had arrived at the station around ten that night.
By the time he met Kaname, he had already been running for nearly three hours.
Judging from Kaname's condition and the distance from the accident site, the train must have derailed after he left the station—which meant that was also when they encountered Akaza.
In other words—
Rengoku had already been fighting Akaza for at least one hour.
Possibly two.
Even though Rengoku had trained as a swordsman since childhood and possessed remarkable talent, his condition must already be declining.
And even if Hiru ran at full speed, it would still take more than half an hour to reach the location Kaname described.
Tanjiro was there as well.
Although he had remained stable so far, he was still a demon who had never consumed human flesh or blood.
Facing such an intense battle, the probability of him losing control was practically one hundred percent.
If Tanjiro were completely swallowed by hunger and destructive urges during the fight…
"Tsc. What a mess…"
Hiru cut off his increasingly chaotic thoughts.
His running speed increased even further.