Kokushibou once again felt jealous of Yoriichi; he had never been able to surpass him in any aspect when he was alive, and he never expected that even after he died, he would still feel frustrated by him again.
He hadn't noticed his mother's discomfort, but Yoriichi had known about it early on and had always accompanied and cared for her. At the time, unaware of this, he even thought Yoriichi was clinging to his mother and acting spoiled, only realizing the truth when he read his mother's diary after her death and Yoriichi's departure.
As for talent and strength, there was even less to say. At only seven years old, Yoriichi, who had never received any instruction, easily defeated the teacher who was teaching him swordsmanship at the time. Yet, the person he could never hit, despite training until his palms bled and calloused, was easily defeated by Yoriichi.
Even now, though he is dead and the Tsugikuni name has vanished into the river of time, his name is still mentioned.
"Even if your body has completely rotted... you are still so outstanding that one can't help but feel jealous..."
Jealousy flared in his heart, and the past humiliations caused by Yoriichi surged forth once more.
Musashi felt that the demon opposite him was not in a normal state. He placed his right hand on the hilt of his Nichirin Sword, ensuring he could draw it at the fastest possible speed.
Although jealous, Kokushibou quickly calmed down, knowing that Yoriichi had long since died.
"Tsugikuni Yoriichi... was my biological brother when I was human..."
Kokushibou answered Musashi's question.
Although he had suspected it, Kokushibou's answer still surprised Musashi.
One brother became a powerful swordsman who protected humanity and nearly annihilated demons, while the other became upper moon one, serving the demon progenitor and harming humans.
"Since you know his name, you must already understand him... But if you weren't in the same era as him, you will never truly understand what kind of person he was, one favored by all gods..."
"I made this choice to catch up to him... Yet, even until his death, I failed to do so..."
As if guessing what Musashi wanted to ask, Kokushibou explained to him first, simultaneously placing his right hand on the hilt of his Nichirin Sword.
"I really still can't understand your way of thinking."
Musashi lowered his eyes after hearing Kokushibou's explanation, gripping his Nichirin Sword tightly with his right hand.
Musashi could never understand the thoughts of these demons. Why could the bonds between humans be so easily discarded by them? Those who were forced to become demons were understandable, but those who willingly transformed into man-eating fiends, Musashi could not comprehend why they would make such a choice.
"If you were to meet him, perhaps you would understand why I made this choice... Someone who has never been jealous of others... It's just that they happened not to meet someone like him, who is favored by all gods..."
Kokushibou defended himself.
To escape the threat of death brought by the Demon Slayer Mark, to reach a higher realm, and to catch up to that person as brilliant as the sun, he killed the Demon Slayer Corps' leader of that generation. With this as his declaration, he met Muzan, transformed into a demon, and gained eternal life.
He didn't believe he had done anything wrong. Once dead, his possibility of catching up to Yoriichi would completely vanish, which made him feel despair. But in the end, even after becoming a demon, he still couldn't catch up to him, and with Yoriichi's death from old age, he lost that possibility forever.
"You are very similar to him... The humiliation and frustration he brought me... I will return to you..."
Kokushibou said, looking at Musashi, gripping the hilt of his blade of vain cries with his right hand, his body slightly sinking downwards as he took an offensive stance.
He knew he could never surpass Yoriichi, but since Yoriichi was already dead, he could not lose to anyone else!
"Moon Breathing, First Form: Dark Moon, Evening Palace!"
The blade of vain cries was unsheathed, and an iaido strike, too fast to see clearly, attacked Musashi, leaving countless tiny crescent blades in its trajectory.
Knowing that Musashi could easily kill Gyokko, Kokushibou held nothing back.
Almost at the instant Kokushibou drew his blade, Musashi also moved. It was also a drawing slash, and the crimson Nichirin Sword was instantly enveloped in scorching flames as it left its sheath.
"Sun Breathing, Waltz."
The arc-shaped slash, entwined with flames, collided with Kokushibou's attack, scattering sparks and moonlight.
However, Musashi ultimately gained the upper hand. Kokushibou's slash, with its tiny crescent blades, was swallowed by the flames, and his body was pushed back two steps.
The moment Musashi drew his blade, the feeling Yoriichi had given Kokushibou reawakened. It was almost the exact same sensation: completely like an ordinary person when not attacking, but once he moved, an extremely strong sense of pressure would arise, like two massive boulders pressing down on his shoulders.
Although the feeling Musashi gave him wasn't as intense, the nature was quite similar.
I have clearly undergone over four hundred years of training, even Yoriichi might not be able to defeat me again, so why was I pushed back by a junior?
The recent setback in their skirmish plunged Kokushibou into doubt; he even found it somewhat unbelievable.
A genius... a person favored by all gods... such talent... why does it not belong to me?
Soon, he understood the reason: the person in front of him was the same type of person as his younger brother.
The veins on Kokushibou's hand gripping the blade of vain cries and on his face bulged, and emotions of jealousy and anger instantly filled his heart.
"I have trained for another four hundred years... It's impossible for me to lose to anyone again!"
"Moon Breathing, Third Form: Loathsome Moon, Chains!"
A large number of crescent blades appeared on the blade of vain cries in Kokushibou's hand. He then swung his blade, releasing two crescent-shaped slashes, accompanied by many smaller crescent blades flying towards Musashi.
The recent clash also made Musashi realize Kokushibou's strength; this was the first demon he had encountered who could directly withstand his techniques.
I can't be careless, or I might die...
Facing the overwhelming barrage of crescent blades, Musashi gripped his Nichirin Sword with both hands. In an instant, three arc-shaped flame slashes flew out, colliding with Kokushibou's moon blades.
Sun Breathing, Second Form: Clear Blue Sky
The two's slashes collided and canceled each other out. Neither Kokushibou nor Musashi missed this opportunity, charging towards each other simultaneously.
The blade of vain cries and the Nichirin Sword clashed, and Musashi felt a hint of surprise. His Bright Red Nichirin, which had never met resistance before, was blocked this time.
But Musashi didn't know that Kokushibou was even more shocked. He could already feel the blade of the opponent's Nichirin Sword cutting into his blade of vain cries. As a weapon forged from his own flesh and blood, he could perceive it, and a burning pain assailed him. However, because the blade of vain cries was an external object, his sensation wasn't intense, but it was still enough to astonish him.
The current situation clearly couldn't continue like this, and Kokushibou immediately thought of a way to resolve it.
Musashi, who was overpowering Kokushibou, suddenly narrowed his eyes. Through the Transparent World, he saw what Kokushibou was about to do. He leaped back a step away from Kokushibou's body, and the instant he moved, a large number of blades suddenly surged out from Kokushibou's body.
If Musashi hadn't retreated that step, he would have been impaled like a porcupine.
"You can indeed see this Transparent World as well... Just like him..."