Kokushibo emphasized the key point.
He lifted his face slightly, his six eyes looking straight through Ryuya—seeing his organs, the flow of his blood, and every minute change inside him.
This was the Transparent World. Within it, everything slowed down—movements, breaths, even thoughts.
That was why Kokushibo always appeared to make instantaneous decisions during their long games of Go.
Only now did Ryuya understand that chess wasn't the real purpose at all.
It was the method his master used to guide him.
"The Transparent World places you in the seat of an observer," Kokushibo explained, his tone calm.
"You attempt to perceive every single movement around you. For example… in this game of chess, if your perspective shifts from 'player' to 'observer,' you will achieve clarity. A doorway to another realm."
This was only the beginning—the embryonic stage of the Transparent World.
Ryuya followed his master's instruction, shifting himself into the position of an observer.
He attempted to embody the board, the pieces, the battlefield beneath his fingertips.
When Kokushibo finally placed the last black stone, the result was predictable—Ryuya still lost miserably.
But—
"Ryuya, you've improved," Kokushibo's faint smile appeared.
Ryuya's talent was extraordinary—surpassing even his own.
A few hints were enough to let him grasp the essence.
Unfortunately, the Transparent World required long-term refinement; it was not something achieved overnight.
"Master, let's play another game!" Ryuya's eyes burned with determination.
His hunger for improvement pleased Kokushibo.
It was Ryuya's talent and willingness to grow that had made Kokushibo choose to teach him Moon Breathing in the first place.
"Good."
Thus began three days and three nights of uninterrupted Go.
"Continue refining yourself. Perhaps sooner than you expect, you may even draw with me."
Kokushibo spoke as he watched Ryuya peeling two lemons.
Ryuya met his gaze and asked, "Master… do you eat lemons?"
"Lemons? Too sour. I don't like them."
Kokushibo lowered his head slightly.
That sourness always reminded him of unpleasant things.
Ryuya's gaze dropped to the small pouch at Kokushibo's waist.
A broken flute peeked out—the same one his younger brother, Tsugikuni Yoriichi, once treasured.
For hundreds of years, Kokushibo had never abandoned it.
"Master, you always keep that flute with you. Is it that precious to you?"
He hadn't expected his apprentice to touch his reverse scale so casually.
Kokushibo's usually still aura stirred.
"Precious?" he repeated.
Seeing Ryuya bite into the lemon, Kokushibo felt the sourness spike.
Was this brat implying something?! No—Ryuya didn't know his story. It must be coincidence.
"If it's not precious, why carry it with you?" Ryuya asked.
"Perhaps." Kokushibo closed his eyes.
To his own surprise, the faint loneliness in his chest made him want to speak. "Do you wish to know the origin of this broken flute?"
"If Master is willing to tell, I'm willing to listen."
Kokushibo quietly told him his story—of envy, inferiority, admiration, and the unyielding brilliance of Tsugikuni Yoriichi.
Ryuya sighed, "So the man Master has been searching for all these years… was your younger brother, Tsugikuni Yoriichi."
Silence.
Kokushibo closed his eyes—not in anger, but in a strange regret.
After centuries, he had finally opened his heart, and speaking of this wound made him feel oddly relieved.
"Master," Ryuya said softly, "you chased the sun all your life. Based on Sun Breathing, you created Moon Breathing.
Even after becoming a demon, you could never reach the brilliance of the sun. But do you know? Although the sun is unreachable… the moon is unique in its own right."
He met Kokushibo's eyes, "To me, Master, the moon is incomparable."
Kokushibo's shoulders trembled. For reasons he couldn't understand, tears filled all six of his eyes.
Demon Slayer Corps Headquarters
Both sides of the room were lined with Hashira-patterned haori.
A composed black-haired youth with dead-fish eyes sat beside a handsome orange-haired young man with silver eyes and a scar near his lip—wearing a tortoise-shell-patterned haori.
They were Water Hashira Giyu Tomioka and Demon Slayer Corps Special Advisor Sabito, reporting directly to Kagaya Ubuyashiki.
Sabito was originally supposed to become the Water Hashira, but he had willingly passed the position to Giyu—believing that Giyu's constant depression needed responsibility to ground him.
This time, Sabito came to report about Makomo and Ryuya.
"Lord Master, should we bring Makomo here and confront her directly?" Sabito asked after giving his full report.
"No need," Kagaya said gently.
A Moon Demon forming a master-apprentice relationship with Makomo… protecting her… and even killing Lower Rank Two for her?
The implications were dangerous.
And the timeline implied Makomo had likely infiltrated the Corps because of the Moon Demon.
If true, the Demon Slayer Corps was in significant danger.
But confronting Makomo would solve nothing.
"Lord Master," Sabito insisted, "if we capture Makomo, we can use her to threaten the Moon Demon and eliminate him altogether!"
Giyu stood silent, staring into the void like usual.
"Giyu," Ubuyashiki asked with a smile, "what do you think?"
Sabito shot Giyu a "don't you dare embarrass me" glare.
"Huh?" Giyu blinked. "…Ah. Yes."
Sabito's eye twitched. "YES?! Giyu, what exactly is 'yes' supposed to mean?! Explain!"
Giyu looked between them slowly, then sighed.
"Sabito, Lord Master… I don't think I'm suited to be here. I'll take my leave first."