"The light of a firefly dares to contend with the bright moon!"
BOOM!
A colossal figure formed of fiery chakra materialized, enveloping Uchiha Nagi's body. It was the Susanoo. At first, it was just a ribcage. Rui's Blood Demon Art struck the Susanoo, penetrating only a few inches before being stopped dead by the bone.
"How... how is this possible?!" Rui was astounded. What was this thing? He had never heard of a Hashira possessing a skill like this, one that resembled a Blood Demon Art.
Then, the skeletal Susanoo swung a flaming longsword—the Sword of Totsuka. With a single strike, it severed all the threads of Rui's Blood Demon Art, the Cutting Thread Rotation.
The Susanoo then began to evolve rapidly—flesh, then an outer garment, finally transforming into a giant the size of a small mountain.
"What... what is this thing?!" Rui muttered to himself.
————
"What's that—?" Giyu Tomioka stared curiously at the giant that had suddenly appeared in the distant forest. Such a towering figure was visible to anyone who wasn't blind.
Arriving at the battlefield, he saw a spider demon woman in a white kimono about to attack the severely injured Tanjiro and Inosuke, who were no longer able to fight.
Tanjiro was immobilized by the after-effects of using the Hinokami Kagura, while the little boar, Inosuke, was also incapacitated due to excessive blood loss and having nearly had his head crushed by the giant spider.
Then, Nezuko, who had been hiding in her wooden box, leaped out to protect her brother, engaging the spider demon.
The Water Hashira, Giyu Tomioka, seeing this, dispatched the demon with a single, swift strike. Afterwards, the reckless little boar, Inosuke, witnessing Giyu's strength, shouted out a challenge.
Giyu promptly tied him up and hung him from a tree. Just as he was about to say a few words to Tanjiro, he saw the energy giant—the Susanoo—appear in the distance.
Of course, none of them knew what it was. They even suspected it might be a technique of one of the Twelve Kizuki, since Hashira were only known to use Breathing Styles.
"That's where Uchiha Nagi-nii is." Tanjiro struggled to get up. "We... we have to go support Nagi-nii."
"No, you just wait here for backup and treatment. Leave it to us." As soon as he finished speaking, the Water Hashira, Giyu Tomioka, vanished, rushing towards the giant with the fastest speed his Water Breathing could afford.
On another side of the battlefield, a woman with a butterfly ornament in her hair also saw it. She was currently tending to Zenitsu.
That unlucky fellow, Zenitsu, had encountered another spider demon and had been secretly bitten by a small spider, nearly dying from the poison.
Fortunately, after he fainted, his subconscious persona had awakened and instantly obliterated the spider demon with a single technique. Then, just as he was weeping in despair over his impending death, his little sparrow, Chuntaro, fluttered its wings and found Shinobu Kocho.
"Moshi moshi~ You should be alright now. I need to hurry over there to help. That giant looks like it won't be easy to deal with. I wonder which rank of the Twelve Kizuki it is," Shinobu Kocho said with a smile, patting Zenitsu's head before leaping away.
Like a butterfly, she utilized her Breathing Style, soaring swiftly towards the yellow giant.
"It's still several times smaller than Madara-sama's~" Uchiha Nagi mused, looking at his own Susanoo. Although it was tens of meters tall, approaching a hundred, it was like comparing a child to an adult when measured against Madara's mountain-sized Susanoo.
He hadn't activated the Susanoo just to show off. Any ninjutsu would have minimal effect on Rui. The demon's physical regeneration was incredibly fast, and its skin was unbelievably tough, comparable to the Third Raikage's.
And every one of the Twelve Kizuki was like this—extremely troublesome. Amaterasu might be useful, but given Rui's regenerative capabilities, he would probably just use his threads to immediately sever any part of his body that was set ablaze, just like the Raikage would.
Even more troublesome was Rui's ranged attack: ubiquitous, incredibly hard, and razor-sharp threads. If Uchiha Nagi were cut by them, he'd be torn limb from limb.
It was better not to use such tactics and conserve energy. Activating the Susanoo's ultimate form was the best option—absolute defense. Clearly, Uchiha Nagi had chosen correctly.
Rui's Blood Demon Art couldn't break through the Susanoo at all; it could only cut through the outermost layer. As Nagi expanded the Susanoo to its full-body form, the demon's attacks became completely useless.
"This, how is this possible!! What kind of technique is this?" Rui, refusing to believe it, unleashed his ultimate attack again.
"Blood Demon Art—Cutting Thread Rotation."
This time, the Blood Demon Art Rui used was even larger, covering the sky and shattering the few remaining trees in the vicinity into splinters with its invisible threads.
[This is bad—] The Water Hashira, Giyu Tomioka, rushing from a distance, witnessed Rui unleashing his Blood Demon Art. The Insect Hashira, Shinobu Kocho, following closely behind him, also sighed inwardly. It was clear that neither of them would make it in time.
Uchiha Nagi, however, laughed wildly. "Hmph, you think you can dance too?"
Uchiha Nagi controlled the Susanoo, raising its exclusive divine weapon, the Sword of Totsuka, and brought it down with force. Although the Sword of Totsuka was a ceremonial blade with little power in its physical state, its might in its spiritual form was immense.
Wielded by the Susanoo, it slashed through Rui's Blood Demon Art, scattering the threads. Then, in the instant Rui, terrified, tried to flee, the sword cleaved him in two.
"Those pierced by the Sword of Totsuka will have their souls sealed within a world of drunken dreams. Go in peace~" Uchiha Nagi stated calmly.
Subsequently, Rui's body began to regenerate, but his eyes were vacant and lifeless. His soul had already been sealed. When the morning sun rose, his body would turn to ash, and he would truly die.
"Moshi moshi, this young man doesn't seem to be one of us from the Demon Slayer Corps, does he? It looks like he just killed a Lower Moon." Shinobu Kocho, light as a feather, slowly descended, though she didn't let down her guard.
For instance, if that mountain-sized Susanoo were to step on them, they'd be turned into meat paste. Humans didn't possess the demons' immortality.
"As long as he's not a demon..." the Water Hashira, Giyu Tomioka, said, his expression unreadable.
Uchiha Nagi, of course, saw them. Arriving with them were Tanjiro and the little boar, Inosuke, both heavily injured but still pushing on to provide support.
"Sugoi... Uchiha Nagi-nii is truly too strong," Tanjiro said, supported by his sister. He and Inosuke had seen the giant even before they got close.
"Bas...bastard! How come so many people are suddenly stronger than me?! This is so frustrating! #" Inosuke fumed. He had wanted to surpass Uchiha Nagi, and now there were two more.
Seeing Uchiha Nagi standing on the Susanoo's forehead, looking like a deity, Inosuke, while furious, also felt a tinge of envy. He fantasized about piloting such a giant himself. Wouldn't he be able to stomp on demons one by one? He imagined himself squashing those things like cockroaches and couldn't help but burst into laughter.
Giyu Tomioka looked at Inosuke and couldn't help but roll his eyes in a deadpan expression. "Is this guy... alright in the head...?"
Seeing that several people had arrived and the most powerful enemy, Rui, had been defeated, Uchiha Nagi naturally deactivated his "Gundam." The Susanoo began to slowly dissipate, and he descended to the ground.
"Greetings, everyone. I am Uchiha Nagi."