Upper Moon One, Kokushibo

As the four of them moved forward, the soft glow of moonlight filtered through the trees, indicating it was early morning, with nearly two hours until sunrise. Suddenly, Ryou sensed something and halted the group.

"Stop," he uttered.

Kanae's expression changed as her senses went on high alert. "Did you find anything?"

"Yes," Ryou confirmed. "Just as Kagaya predicted, there's a manor about a kilometer from here. But Muzan isn't there—only a house filled with corpses. And there's a powerful demon waiting for us."

"Is it an Upper Moon?" Kanae asked.

"Far stronger than an Upper Moon Demon," Ryou replied calmly.

Kanae took a deep breath, weighing the situation. She knew they couldn't afford to lose track of Muzan, not after the Demon Slayer Corps had finally uncovered his trace after so many years.

"How confident are you in dealing with that demon?" she asked.

"I won't lose," Ryou stated.

After a moment's thought, Kanae said. "Let's do it. We can't miss this opportunity to find Muzan's traces!"

--

It didn't take long for them to reach the manor, but as they approached, the atmosphere around them changed. The air grew colder, and the traces of demon presence became more apparent.

Suddenly, a chilling breeze swept through them, carrying an overwhelming sense of malice that sent a shiver down their spines.

Kanae's hand instinctively moved to the hilt of her Nichirin sword, her expression turning serious. Tatsuya and Haruka mirrored her actions as they prepared for the upcoming confrontation.

In contrast, Ryou remained calm, his demeanor nonchalant, as if he didn't sense the demons.

From the shadows, figures began to emerge—several twisted demons, their grotesque forms barely resembling ordinary demons. They weren't just any ordinary demons; their presence was on a different level, only slightly weaker than Lower Moons.

Ryou, Kanae, Tatsuya, and Haruka immediately sensed the difference. 

"Be careful, Haruka. These demons give me chilling vibes," Tatsuya muttered audibly, his stormy gray eyes narrowing as he gripped his sword, ready to draw it at a moment's notice.

"Yes," Haruka responded, drawing her sword and holding it firmly with both hands, her stance steady.

Suddenly, Ryou's eyes sharpened as he took a step forward. "You three, get behind me," he ordered, his serious voice startled them.

Without hesitation, Kanae, Tatsuya, and Haruka moved behind him. Just as Kanae was about to ask why, they felt a surge of ominous energy—so intense that it made their blood run cold.

The air grew so heavy it felt suffocating, making it difficult to breathe, as Kokushibo, Upper-Rank One, emerged from inside the manor. His presence was menacing and overwhelming.

The tall, imposing figure, with six glowing eyes, seemed to pierce through the four of them. His long dark hair, tipped with red, flowed like a shadow, and the ominous katana at his side gave him the fearsome aura of a warrior.

Aside from Ryou, the presence of Kokushibo made the three others tremble on their feet, nearly losing their will to fight. The sheer terror made them consider throwing their swords down and running away.

At that moment, Ryou chuckled. "You've surely got the presence of an Upper Moon One. If it were any weaker, I'd be quite disappointed."

His words snapped the other three out of their fear, helping them regain their composure as they faced the Upper Moon One.

Kanae's eyes widened as she realized who stood before them. "Upper Moon One..."

"It's just as Muzan-sama predicted," Kokushibo muttered, his six cold eyes fixed on them. "The current Ubuyashiki is truly a man of action, sending two of his best Hashira. And it's been a while since I've encountered a human who could stand before me without a trace of fear.

But you're too late. Muzan-sama is not here."

The demons began to circle the four of them, their eyes filled with desire to devour. Their appearance and hunger made it clear they were newly created.

"We are being surrounded," Haruka said.

Ryou spoke as his eyes fixed on Kokushibo. "I'll handle the Upper Moon One. Tatsuya, Haruka—you two are responsible for clearing the other demons. Kanae, don't help them. They need the experience. Just watch from the side."

"Be careful, Ryou," Kanae nodded, her voice calm despite the situation. She knew Ryou's strength better than anyone.

After his words, the battle erupted. Tatsuya drew his sword and unleashed his Storm Breathing, slicing through the air with rapid, powerful sword slashes that cut down the demons with ease.

At the same time, Haruka also sprang into action. The simplified Nature Breathing allowed her to behead the demons with precise moves.

Meanwhile, Kanae observed their battle with focus, ready to act if they were in danger. Although Ryou had told her not to assist them, she wouldn't sit by if something unexpected, endangered Tatsuya or Haruka.

--

"Blind arrogance," Kokushibo muttered unhurriedly, his voice dripping with disdain. "You think you can stand against me? A mere Hashira is no match for an Upper Moon."

"I'm not a mere Hashira," Ryou responded with a teasing smile. He then gestured with his right hand, inviting Kokushibo to attack, while his left hand remained casually behind his back. "Why don't you try?"

His provocative actions even managed to irritate the usually calm Kokushibo. How could a mere human dare challenge him—was he even worthy?

Ryou and Kokushibo's gazes locked, the tension between them palpable. The air around them crackled with energy, and the atmosphere grew heavy under the immense pressure.

Without a word, Kokushibo unsheathed his blade—a blood-red katana with a veiny appearance, its blade covered in countless eyes. The weapon exuded an ominous presence, distorting the air around it with the sheer power it radiated.

"Clang!"

The battle began with a resounding clash of blades. In a flash, Kokushibo appeared before Ryou, his sword slicing through the air with incredible speed. Ryou drew his Nichirin sword with lightning-fast speed and parried the strike.

The force of the blow sent a shockwave through the air, rippling outward with them as the center.

After a brief but intense clash, both Ryou and Kokushibo leaped back, momentarily ending their blow.

"You're not bad," Kokushibo remarked. "Tell me your name..."

"Nature Hashira, Ryou," he replied.