When Yosuke returned to the Butterfly Mansion, he found a fierce sparring match underway.
The two combatants were Hakuji and Kyojuro Rengoku, who had just completed a mission and stopped by to visit Tanjiro and his friends.
They were fighting with full vigor, both wearing broad smiles.
Hakuji called out between strikes, his voice full of admiration:
"Kyojuro, you've gotten even stronger!"
Rengoku, beaming with his signature grin, laughed heartily.
"Not enough yet! I can tell—you're still not fighting at full strength, Hakuji!"
"It's almost dawn," Hakuji said, his eyes gleaming. "Kyojuro, let's end this spar with our strongest techniques!"
"Very well!" Rengoku agreed with blazing enthusiasm.
"Soryu Technique – Destructive Death: Final Form – Azure Silver Chaos Flash!"
Summoning the Compass of Destruction, Hakuji unleashed hundreds of energy blasts in every direction, radiating outward from his body in an instant.
"Flame Breathing, Ninth Form: Rengoku!"
In response, Rengoku swung his Nichirin Blade, his strike burning with hellish fire. The inferno obliterated Hakuji's projectiles and surged toward him with unstoppable force.
In the next instant, the entire Butterfly Mansion was engulfed in smoke and debris.
When the haze cleared, Hakuji's body bore extensive burn marks, while Rengoku's haori had been completely destroyed.
Hakuji's burns healed almost instantly. "Incredible, Kyojuro," he said, awe in his tone.
Rengoku, however, shook his head. "You held back, Hakuji. Though I destroyed most of your blasts, a few should have struck me. But just as they were about to hit, they veered away."
Hakuji laughed warmly and slung an arm over Rengoku's shoulder.
"Don't sweat the details. I'm a demon—you're human. You were at a natural disadvantage from the start. I just wanted us to fight on even ground."
At that moment, Tanjiro, Zenitsu, and Inosuke burst from the sidelines, eyes shining with admiration as they looked up to both warriors.
"Big bro! Third bro! You're both amazing!"
During Yosuke's recent stay at the Ubuyashiki estate, Hakuji and Rengoku had returned to the Butterfly Mansion, where Tanjiro and his friends had been training under their joint guidance.
Their overwhelming strength and openhearted natures made the trio deeply admire them.
Yousuke smiled softly at the scene, choosing not to interrupt. Instead, he went to the laboratory where the Butterfly Sisters and Tamayo were conducting research.
He handed them a vial of blood.
Shinobu tilted her head curiously. "Master, is this blood from one of the Twelve Kizuki?"
Yosuke shook his head. "No—it's from Amane Ubuyashiki, Kagaya's wife."
Kanae frowned slightly. "Amane Ubuyashiki? But she's an ordinary human, isn't she? Would her blood even have research value?"
"Amane is a member of the Divine Priest family," Yousuke explained. "I'd like you to examine this sample to see if there's any unique power within it."
Remembering what Yosuke had told them earlier about his suspicions, the women understood his intent. They immediately began analyzing Amane's blood.
Meanwhile, in the Infinity Castle—
Inatama Kain appeared before Kibutsuji Muzan.
Since becoming a demon, Inatama's power had grown rapidly, earning Muzan's approval. Though still weaker than the Upper Moons, he had been appointed as a temporary replacement for the deceased Lower Rank One, Enmu.
Muzan granted him another infusion of blood, further increasing his strength.
Confident in his abilities, Inatama believed that, with two Upper Moon positions now vacant, it was only a matter of time before he rose to that rank himself.
Muzan perused the Ubuyashiki clan documents that Inatama had stolen, his eyes flashing with cold light.
"So that's how it is… After that great battle, the Demon Slayer Corps and the Ubuyashiki clan hid themselves at Mount Akaiiwa?"
He turned his gaze toward Kokushibo. "Kokushibo, go to Mount Akaiiwa. Find out if there are any traces of the Divine Priest family there."
Expressionless as ever, Kokushibo bowed. "As you command."
L
A few days later, the Butterfly Sisters and Tamayo hurriedly sought out Yosuke. They had made a breakthrough in their research on Amane Ubuyashiki's blood.
"Amane's blood is extraordinary," Shinobu reported. "It contains a power that can suppress Kibutsuji Muzan's blood."
Yosuke nodded calmly, unsurprised. But the next piece of information left him utterly shocked.
"When we compared her blood with Nezuko's," Tamayo continued, "excluding Muzan's demonic influence, the rest of their blood composition was almost identical."
The revelation hit Yosuke like a thunderclap.
He vividly remembered the first time he met Tanjiro and Nezuko—he had sensed that within Nezuko's body flowed a warm, radiant energy, remarkably similar to the power of the Sun Breathing technique.
At the time, Yousuke had assumed that when Tsugikuni Yoriichi taught Sun Breathing to Tanjiro's ancestor, Sumiyoshi Kamado, the technique had, over generations, left traces of its essence in their bloodline.
But this new discovery shattered that assumption.
Thinking carefully now, it made sense to question everything.
Why was the Kamado family able to perfectly preserve the Dance of the Fire God for generations?
Why could Tanjiro himself wield Sun Breathing?
And why was Nezuko's blood nearly identical to Amane Ubuyashiki's?
There could only be one truth.
When Yoriichi passed Sun Breathing to Sumiyoshi, a member of the Divine Priest family must have married into the Kamado bloodline. Their descendants inherited the innate ability to use Sun Breathing.
From this truth, one could infer even more: perhaps Yoriichi's own ancestors had once intermarried with the Divine Priest family—making Yoriichi himself a descendant of both the Tsugikuni line and the Divine Priests.
That would explain everything—
Why Yoriichi was born with the ability to perceive the Transparent World and manifest the Demon Slayer Mark.
Why Tanjiro could wield Sun Breathing.
Why Nezuko could suppress Muzan's demonic blood.
Because within their veins flowed the power of the Divine Priest bloodline.
The Divine Priests had seemed absent from history, yet now, Yousuke realized—they had been everywhere all along.
The thought sent a chill crawling down his spine.
"Master…? Master!" Shinobu's worried voice broke through his dark thoughts.
Yosuke blinked and looked up to see the anxious faces of Shinobu, Kanae, and Tamayo before him. Forcing a faint smile, he said, "I'm fine. Just… surprised, that's all."
"I'm surprised too," Shinobu said. "Who would've thought that two completely unrelated people could have identical blood?"
Yosuke wanted to tell them that Nezuko and Amane were connected by blood—but the words stopped at his lips.
The truth was far too fantastical. Telling them now would only cause confusion and worry.
After some thought, Yosuke spok
e quietly:
"I may be away for a while. I'm going to Mount Akaiiwa. Perhaps there, I can uncover traces of the Divine Priest family."