Pffft—!
That head, wearing an expression of disbelief and terror, flew high into the air.
"Thunder Breathing: Seventh Form: God of Fire Thunder—!!"
"How is this possible! This technique... why have I never seen it before!!"
"As expected, that old man really did teach you his ultimate technique! That bastard!!"
Kaigaku's severed head, as it plummeted into the abyss, stared at the golden figure still maintaining his sword-swinging posture on the crumbling wall. The jealousy in his heart reached its peak as he continued to curse incessantly.
Having unleashed this technique, Zenitsu was also completely exhausted, tottering on the edge of the platform:
"You're wrong... Senpai..."
"This wasn't taught to me by Gramps. This is my own form...."
"I really wanted to use this technique... to fight alongside you...."
Kaigaku's head was rapidly burning away. His life had reached its end.
"How is that possible! A waste like you can create your own sword form? Don't make me laugh!"
"Cough… ah—!!"
Zenitsu suddenly trembled violently. Mouthful after mouthful of blood gushed from his mouth.
God of Fire Thunder was the ultimate of Thunder Breathing's essence. The burden on the body had surpassed human limits.
Added to the multiple forced uses of Thunderclap and Flash in the previous battle, the pain within his body was now unbearable.
Muscles tore. The bones in his lower leg shattered to pieces.
He could no longer hold on.
"It's over... Gramps...."
Zenitsu's vision began to blur. He felt his body tilting backward.
The section of corridor he was on had completely collapsed. Below was the Infinity Castle's bottomless abyss, leading to nothingness.
With his legs already numb, he couldn't even make any adjustments.
Zenitsu thought of his master, that old man who leaned on a cane, always stern-faced yet would give him rice balls when he cried.
"I'm sorry, Gramps... I'm still... so useless."
"Haha! Even if you created it yourself, so what! Falling from this height, you'll die with me!"
"In the end, the old man's Thunder Breathing will still be lost! Serves you right!"
".....It will not be lost, child."
Just as Kaigaku was cursing endlessly, a figure he could not imagine shot up like lightning, steadily catching the falling Zenitsu.
"Th-this... how is this possible...."
Kaigaku's voice completely dissipated in the ashes, leaving no trace of his existence behind.
"Who..."
Zenitsu struggled to open his eyes.
In a blur of tears, he saw an illusory yet clear figure.
It was an old man wearing a yellowish-brown kimono, his face stern yet radiating infinite compassion.
Kuwajima Jigoro.
His powerful hands, year-round calloused from gripping his sword, now tightly supported Zenitsu's shoulders, providing the final support for his tottering body.
"Gramps...?"
Zenitsu was stunned.
He knew Gramps was dead, having died alone in that agonizing seppuku.
But now, the warmth transmitted from those palms...
That familiar scent, faintly carrying the smell of tobacco, was so real.
"....Well done, Zenitsu."
The old man's steady voice sounded before Zenitsu.
"You are not useless! You are the disciple this old man is most proud of in his entire life!"
Those powerful hands gently patted Zenitsu's head.
Just like under that massive peach tree, countless times when he encouraged him to persevere.
"Wah... Waaaaahhhhh!"
On this cruel battlefield, on the edge of this collapsing Infinity Castle.
That newly risen strong one who had killed an Upper Moon demon now, like a three-year-old child, tightly clung to the old man's figure, letting out a heart-wrenching cry.
Time rewound to a few days prior.
When Jigoro resolved to commit seppuku, he had asked Taka:
"....Storm Hashira, would you be willing to act as my kaishakunin?"
"What does kaishakunin mean?"
"A person committing seppuku suffers immensely. Even though this old man's heart is as firm as iron, it's hard to avoid feeling fear... I'm worried I might not be able to go through with it. I ask you, after I thrust into my abdomen, to sever my head... grant me a quick death!"
".....I will not." Taka calmly rejected the proposal. "I made a promise. My blade does not kill humans."
"....Is that so? My apologies, for making you hear such a difficult request."
Jigoro no longer pressed. He had made his final decision.
Shing—!!
This strike, filled with death, was fast and fierce. He was confident it would directly pierce his abdominal cavity, leaving no chance for lingering on!
But that excruciating pain never came. The blade tip only cut the skin of his abdomen.
Jigoro looked at the blade in shock, finding Taka's speed so incredible that he had grabbed the blade the moment he thrust it towards himself!
Blood continuously dripped from Taka's palm, quickly staining the ground before Jigoro.
Both shocked and angry, he looked darkly at Taka: "....Storm Hashira, what are you doing! Are you insulting this old man!"
"Old man, I really don't understand what you're doing."
Taka's hand was very strong. No matter how Jigoro struggled, he could not free the blade from his grasp.
"Dying is the easiest thing. Living is the true hell."
"That's right. Your disciple became a demon. The Thunder Breathing swordsman you painstakingly nurtured became a nightmare for the Demon Slayer Corps. So you intend to die by suicide and escape this matter?"
"Disgracing Thunder Breathing, so you must atone with death? Don't be ridiculous, old man. The dead have no right to define these things. Only the living can pass judgment on them."
Seeing Jigoro's gaze begin to flicker, Taka exerted force and directly snatched his blade away.
"Perhaps your master will lament your death. Perhaps your comrades will admire your fortitude. But those peripheral members of the Demon Slayer Corps who don't know you well will only treat this matter as fleeting clouds. No one will care about the glory of Thunder Breathing."
"And what about Zenitsu? You'll be gone, but he will remember this for his entire life. Every time he thinks of it in the future, he will be agonized. Is this the result you want to see?"
"This old man... how could this old man mean that!" Being spoken to like this by Taka, thinking of Zenitsu's tearful state, Jigoro's expression darkened. He quickly tried to defend himself.
Taka tossed the blade aside and used a torn strip of cloth to bandage the wound on his palm. "But the result is not decided by you, a dead man."
"Instead of thinking about escaping everything through death, why not fulfill your responsibility as the Rumble Hashira and risk your life to fight Kibutsuji Muzan!"
"You only have one life. Don't let it be lost meaninglessly!"
That night, Taka said many things. He himself hadn't expected to be able to utter so much wisdom.
But thinking about it carefully, these were merely his genuine feelings, evoked by watching Jigoro not cherish his precious life.
The two sat and talked at length. In the end, he persuaded Jigoro to abandon the idea of suicide.
But he proposed a suggestion.
"Zenitsu has great potential, but he has always lacked the resolve to fight. I think we can give him a push."
In Taka's plan, Jigoro would inform Oyakata-sama of his faked death, and Oyakata-sama would announce his death to Zenitsu.
With such an immense stimulus, whether Zenitsu would sink into despair or be completely reborn, Jigoro would observe from the shadows.
If Zenitsu truly could not bear the blow, he would timely appear and explain everything. At worst, master and disciple would fight to the death and both perish in the Infinity Castle!
But now, looking at Zenitsu, covered in wounds, who had slain an Upper Moon Kizuki, Jigoro's tears fell uncontrollably.
"It's over... child! You are my pride!"
Meanwhile, outside the Infinity Castle.
The former Flame Hashira, Rengoku Shinjuro, along with Uzui Tengen, who had recovered from the potent poison but lost an eye, stood guard outside the door of the new Oyakata-sama, Ubuyashiki Kiriya.
"Success! Another Upper Moon defeated!"
Kiriya's excited voice came from inside the room, also catching Tengen's attention.
"Ah... these Upper Moons seem quite easy to kill... How come two have died in such a short time? I really want to join the battle spectacularly..."
He turned his head and looked at the silent, neatly dressed Shinjuro: "Guess which Upper Rank it was? Upper Rank Five just died. Could this one be a higher rank?"
Before Shinjuro could reply, a Kakushi member inside the room released a Kasugai Crow to announce to the surrounding on-guard members—
"Agatsuma Zenitsu! Upper Rank Six! Defeated!!"
'Who?' Tengen only felt a sense of unreality.