When Yoriichi received a letter from Hiru, he was genuinely taken aback. If Hiru had anything urgent to report, he would have transformed into his demon form and come to him immediately—Yoriichi would naturally have rushed to meet him.
As for matters that weren't pressing, Hiru preferred to handle them on his own at a leisurely pace. By any measure, this was the first letter Yoriichi had ever received from him.
Yet as he read it, Yoriichi couldn't help letting out a quiet murmur of surprise.
"Amida Butsu… Has something happened?" Himejima asked.
"Mm… I suppose you could call it something interesting," Yoriichi said with a smile. "Hiru says he's discovered someone like me—someone born with mastery of the Transparent World, who also uses Sun Breathing."
"That is truly excellent," Himejima said, bringing his hands together in prayer. "But… what exactly is this Transparent World?"
"That's precisely what I wanted to explain to you. The Transparent World is a realm one can reach after becoming proficient with Aura—by using Aura to control one's senses. In that state, it becomes easy to see through an opponent's movements."
Although you've already grasped Aura to a basic degree and qualify to advance further, I'm not certain whether physical blindness would affect how the Transparent World manifests.
"I see… Then what does it look like, exactly?"
"Simply put, you can see the opponent's muscles, bones, and even their inter—hmm?"
"What is it?"
"No, nothing." Yoriichi shook his head lightly. "Let's set aside the matter of the Transparent World for now. You should first become thoroughly familiar with sensing Aura."
"Yes… I was being too hasty," Himejima replied calmly.
[If it's only Aura sensing, it could be explained as a matter of constitution. But if one can truly see… then Hiru's situation becomes much harder to explain.]
Yoriichi frowned, then suddenly realized something and lowered his gaze back to the letter, reading it again.
[Wait—Hiru said he found someone who is both innately transparent and capable of Sun Breathing?]
The moment this sank in, two complicated emotions rose within Yoriichi. One was relief—that someone who surpassed him had finally appeared. The other was concern—that his younger brother might be shaken after having his identity exposed.
These feelings tangled together, leaving Yoriichi in a rare state of inner turmoil.
[To think another person who mastered both the Transparent World and Sun Breathing would be a descendant of Mr. Sumiyoshi… Even if it took centuries, it proves that humanity will never lose to demons. To witness this firsthand is deeply moving. If only I could fight alongside such a successor.
No—that isn't what matters. If that successor is innately transparent like me, then someone who has already formed a complete worldview would surely be terrified upon seeing Hiru's condition… Wouldn't the two of them end up fighting?
No—more than likely, they would. After all, even when I was human, seeing Muzan filled me with a bone-deep chill. That instinctive dread, born of the body itself, cannot be suppressed…
Mm… Since Himejima has already learned to use Aura, perhaps I should return and ask Hiru directly. I only hope Hiru wasn't hurt by the other's reaction.]
Himejima tilted his head slightly toward Yoriichi, whose Aura was fluctuating faintly.
"If it troubles you, then you should go and see him. At the start of the new year, being with one's family is what matters most."
Yoriichi came back to himself and smiled apologetically, nodding.
"My apologies—I was lost in thought. You're right. I should return."
"Please give my regards to Yukinashi."
"I will." Yoriichi folded the letter and put it away. "Before that, let's spar one last time. Our next meeting will be the first Hashira Gathering after the New Year."
"Hm." Himejima smiled as he stepped toward the training grounds. "Perhaps some new blood will join us. That alone is worth looking forward to."
"Yes," Yoriichi agreed softly. "It truly is."
...
After returning to the small valley where Yukinashi lived, Yoriichi first collected the backlog of accumulated missions from him. Then, after enduring Yuichiro's thinly veiled disdain and Muichiro's unhidden longing, he immersed himself in clearing out the remaining work.
By the time he finished and returned, he found Yoriichi teaching Aoba and the two children how to use [Aura].
Hiru unceremoniously pulled Aoba out of the group.
"Kanao was taken away?"
"Yes. Shinobu came to get her," Aoba said, wiping the light sheen of sweat from his forehead. "You were pretty quick."
"As long as I see them, I can tell whether they're demons. And if I carry the medicine, demons will come out on their own," Hiru replied, scanning the surroundings. "This place has a nice environment. How about I build a house here?"
"What, decided to be my neighbor?" Aoba laughed. "I thought your hometown wasn't anywhere near here."
"Mm—at least for now, I don't plan on going back there," Hiru said, watching Yoriichi arrange training for the twins. "I have a bad feeling about it."
"Bad feeling?" Aoba looked puzzled, then suddenly understood. "Ah… because of your older brother?"
"Yeah…"
"I can't really offer much comfort," Aoba said, glancing at Yoriichi as he approached, then patting Hiru on the shoulder. "If you want to live here, feel free. I'm more or less used to taking care of kids anyway."
"Haha. When you put it that way, I do suddenly feel a bit sorry."
"Oh? So you actually know how to apologize," Aoba teased.
Watching the two of them bicker in lowered voices to preserve appearances in front of the children, Yoriichi smiled faintly.
"Looks like I'll be imposing on you for a while."
"Haha! If anything, I'm the one getting the better deal—being neighbors with Yoriichi," Aoba said with a hearty laugh. "Those guys should be green with envy that I can ask you for guidance whenever I like."
"You two probably have things to talk about, so I'll head into the mountains and check the traps. I won't disturb you."
"Alright. Thanks. I'll cook later," Yoriichi said.
"Haha, that's something to look forward to—Yoriichi's cooking."
Once Aoba had gone some distance away, Hiru finally spoke again.
"So… you received the letter, Brother?"
"Yes. I came back after reading it," Yoriichi replied, turning his gaze toward him. "Is he truly Mr. Sumiyoshi's descendant?"
"Of course. Honestly, it startled me too," Hiru said, unconsciously touching the side of his neck. "If this weren't such a peaceful era, with everyone lacking martial conditioning, I might have lost my head right there. His movements were hardly inferior to yours."
"To how I am now?" Yoriichi asked.
"From your human days," Hiru lowered his voice. "You know humans can't compare to demons physically."
"Mm…"
"There's one major difference between him and you, though. His body is extremely weak—by the look of it, he might only have a year or two left."
"Was he born without a healthy body?" Yoriichi paused, regret coloring his tone. "Is there no way to treat him?"
"Even with careful treatment, he wouldn't live past ten. His body has already been pushed to its limit by the Breathing Techniques," Hiru said with a dismissive wave. "And more importantly, there's no way to build trust. I'm not even allowed close to him, so treatment is out of the question."
"I see…" Yoriichi sighed. "If one can see everything so clearly, trust really would be impossible to establish."
Hiru let out a quiet sigh as well.
"Honestly, I never imagined someone like that would appear. And even if they did, it shouldn't have been in this country."
"How can you say that?" Yoriichi replied gently. "There will always be people in this world who surpass me."
"Yes—I know, I know," Hiru said, dragging out the words as he glanced at Yukinashi returning with a deer slung over his shoulder. "But for now, let's eat. Dinner!"
Watching Hiru dash off toward Yukinashi, Yoriichi shook his head helplessly. After a brief silence, he turned his gaze toward the direction where Mount Kumotori lay in his memories.
"…Will there ever come a day when we can fight side by side?"