"Who's there?!"
Shuya's guard shot to maximum. His eyes snapped toward the source of the voice.
A complete stranger had gotten right next to him without him noticing. That alone was shocking.
Standing in front of him was a tall man with long crimson hair, wearing a red haori. A flame-like crimson pattern glowed on his forehead. His calm, slightly melancholic eyes carried an air of quiet invincibility just by standing there.
The name slipped out of Shuya's mouth before he could stop it.
"Yoriichi Tsugikuni?"
"You can see me?"
Yoriichi's calm expression cracked. His gaze sharpened with sudden intensity.
"No way…"
Shuya froze for a second, remembering the conversation he'd had with Saeko last night back in Greed Island. They'd been talking about the secrets of Breathing Styles, and he'd jokingly thought to himself that Sun Breathing probably didn't come with the ability to see Yoriichi Tsugikuni.
Turns out… it actually did.
Shuya stared at the crimson figure. With his abilities, he could tell right away—this was the same kind of lingering soul as Makomo and Kanae. A post-mortem Nen spirit.
Except the power radiating from this man was on a completely different level.
"Junior… can we talk?"
Yoriichi was just as shocked as Shuya. In the centuries since his death, Shuya was the first person who could actually see him.
"Of course."
Shuya agreed immediately. He was burning with curiosity about this legendary figure. In combat alone, Yoriichi was the undisputed ceiling of the Demon Slayer world—Muzan himself had acknowledged it. Born with the Mark and Transparent World, he had also created the entire Breathing Style system that let normal humans fight demons.
Shuya had long suspected Yoriichi was a natural-born Nen user. This guy was basically a walking treasure chest.
His Equivalent Exchange ability was already itching to activate.
Come on, old man. Drop the gold coins.
Yoriichi asked the classic isekai question first.
"Junior… what year is it now?"
"Roughly three hundred years since you died."
Shuya kept his excitement in check and answered calmly. Yoriichi had lived during the Sengoku period—over four hundred years ago—but unlike other Marked swordsmen, he'd lived all the way to his eighties before passing peacefully.
"Three hundred years already…? Time really does fly."
Yoriichi gazed into the distance, voice soft. "After all this time… are you still doing well, big brother?"
He turned back to Shuya, a hint of nostalgia in his eyes. "I can feel the presence of Sun Breathing on you. Are you a descendant of Sumiyoshi?"
"I'm not. But I do know his descendants. I learned Sun Breathing from them."
"I see."
A flicker of disappointment crossed Yoriichi's face at the failed connection attempt. Then he asked the question that clearly weighed on him the most.
"What about the Twelve Kizuki under Muzan right now—?"
Shuya didn't let him finish.
"You actually want to know about your older brother, Michikatsu Tsugikuni, right?"
"You know?"
Yoriichi's eyes widened. He didn't deny it. "Please… tell me everything you can about my brother."
"After you died, your brother became Upper Rank One—the second strongest demon under Muzan. He's spent centuries chasing the pinnacle of swordsmanship, trying to surpass you, his little brother."
Yoriichi let out a long, heavy sigh.
Shuya cut through the melancholy. "I've told you what you wanted to know. Now can you answer my question?"
"Go ahead."
Shuya didn't hesitate. "Are you a Nen user?"
"Nen user?"
Yoriichi repeated the words, clearly confused. "What is that?"
Shuya wasn't surprised. He gave a quick explanation of Nen and aura.
"I see… That explains it."
Understanding dawned on Yoriichi's face. No wonder controlling life energy came so naturally to him while everyone else struggled. He'd only been able to teach others by using Transparent World to observe the changes in his own body and turning it into Breathing Styles.
If he really was a natural-born Nen user, everything made sense.
But…
What was his Nen ability?
Yoriichi thought for a moment, then pointed at the crimson pattern on his forehead.
"Probably the Demon Slayer Mark?"
"The Mark?"
Shuya raised an eyebrow. On second thought, it actually fit. The Mark and Transparent World were things Yoriichi had been born with. Transparent World was more of a technique—like the Four Major Principles—while the Mark had been completely unique to him before he created Breathing Styles.
No one else had ever awakened it until they trained in his system. And unlike everyone else who got the Mark, Yoriichi had lived a full life into his eighties. That alone proved his version was special.
More importantly, Yoriichi's only remaining regrets were Muzan and his brother Kokushibo.
For Shuya, taking care of both was basically a side quest.
"Your regrets are Muzan and your brother Michikatsu, right? How about a trade?"
Shuya smiled. "My Nen ability is called Equivalent Exchange. I help you fulfill your regrets… and in return, you give me your Nen ability. Deal?"
Yoriichi looked at him for a long moment, then slowly shook his head.
"You're too weak."