A few days passed like that, and just as Nezuko's consultations were stabilizing, 'Giyu Tomioka' came to visit.
"Long time no see, Sword Saint. I still haven't forgotten you grabbing my head."
"I see. So, have you come for revenge?"
At my question, Giyu shook his head and said, "No, I have no such intention. It was just so shocking that all my years of accumulated effort were completely useless against you. That aside, let me ask you one thing. Is there anyone stronger than you?"
"Not that I know. But you never know. The world is wide, so there might be."
At that, Giyu sighed.
"Hoo... I really am no different from a frog in a well, just as you said."
I first showed Giyu to his lodgings, and since he had come from far away, I prepared a meal for him. While eating, I also asked Giyu something I was curious about.
"I hear the number of demons has increased lately. Is the Demon Slayer Corps doing alright?"
"Although they were Lower Moons, Shinobu and Tengen each killed one of the Twelve Kizuki. Since then, I don't know what's gotten into Muzan, but he's started increasing the number of demons. So casualties among the lower-ranked members are considerable. Because of that, the Hashira are working hard."
Hearing that they had even killed Lower Moons, it seemed that the Hashira had become stronger from my training, differing a bit from the original story.
"Then, it must be hard for you to come here, being busy."
"That's not the case. Although it's only a month, the Hashira who learned from you have definitely become stronger. The Master seemed to think it was worth sending us."
"I see. Understood."
From that day, I taught Giyu and Nezuko together. Although their skill levels differed, since they both used Water Breathing, it would likely be very helpful for Nezuko as well.
"Water Breathing is primarily composed of soft, flexible techniques. So, I created this technique to see if I could maximize that flexibility. Nezuko, stand up and attack me."
"Yes."
Nezuko stood up and swung her wooden sword down, aiming for my head. I immediately blocked with my sword, then used her force to spin my body, counterattacking and stopping the strike right in front of her. I had used her attack to spin and counterattack immediately.
As I counterattacked quickly, she seemed quite surprised. Giyu was contemplating the technique I had just demonstrated.
"Using the opponent's force... Then, if the opponent uses a big technique, the speed and power would be even greater."
"That's right. But there are also drawbacks. The opponent must use a big technique, and the timing must be perfect. Only when both conditions are met does the technique work properly. If you become skilled at this, you can attack before the opponent can sheathe their sword, making it an extremely threatening move."
In short, it was a counterattack technique using the sword.
"So you two will now practice this technique by dividing roles into attacker and counterattacker."
"Hmm... I understand. But I heard the young girl is working as a doctor here. Does she have time?"
When he asked about Nezuko's time, I answered, "During the day, whenever I have time, I'll refine your swordsmanship, and from evening, after consultations are over, you two can practice."
"I see. Understood."
When training began, as befitting a Hashira, Giyu quickly mastered it. But Nezuko was also able to learn it shortly after. It seemed to be the power of her [Swordsmanship] ability. Although the two were still clumsy, they quickly began to get used to it.
A month later, Giyu packed his bags and prepared to leave. Having trained together, Nezuko seemed to have grown a bit attached to him and saw him off.
"Nezuko, thank you for helping with the training."
"Not at all. I also learned a lot. I should be thanking you."
"Then, see you later. Sword Saint, Nezuko."
After Giyu left the clinic, the final Hashira, 'Muichiro Tokito', arrived. But he didn't come alone—'Sanemi Shinazugawa', and the Ubuyashiki eldest and second daughters, 'Hinaki' and 'Nichika', came with him.
"Why the big group this time?"
At my question, the eldest daughter, Hinaki, explained.
"This time, 'Gyomei Himejima' captured an Upper Moon of the Twelve Kizuki, and 'Kyojuro Rengoku' also captured a Lower Moon."
Then the second daughter, Nichika, continued, "The Master received instructions to 'serve the Sword Saint, who is doing what I cannot'."
She then handed me a letter. Inside, it contained a request to continue the legacy of Total Concentration Breathing if the Demon Slayer Corps were annihilated, and a plea to definitely capture Muzan even if he himself died. Finally, it said to take good care of his daughters. It seemed Kagaya was already preparing for his own death.
"You are still young. Return to your families."
When I said that, Hinaki and Nichika suddenly prostrated themselves before me, clearly explaining the reason for their coming and asking me not to refuse.
"We are an arrangement in case everything fails. So please, do not refuse us."
After they spoke, Sanemi placed a large box he had been carrying in front of me. Inside were enormous amounts of cash and various land deeds. It was enough money to create another Demon Slayer Corps and run it for a long time. In short, Kagaya seemed to be using me as insurance.
"Honestly... Fine. Get up. By the way, you, Sashimi? Why are you here?"
When I pointed at Sanemi and asked, he got angry at being called 'Sashimi', his veins bulging on his forehead. After calming down for a moment, he said to me, "Hoo... It's Sanemi, not Sashimi. I came to escort them and deliver the items. Also, I want you to make me stronger."
"Why? I already told you everything you needed to fix."
"Well..."
When Sanemi hesitated, Muichiro answered for him. "Because you lost to Obanai last time."
At that, Sanemi flared up. "You brat!"
"It's not like I said anything wrong."
From what I heard, Sanemi had been badly beaten in a spar with Obanai. I swallowed a laugh inwardly and looked to the side. I noticed that the Ubuyashiki sisters had quietly approached and were standing on either side of me, as if guarding me. They were children who hardly made any sound.
'Really, they're like ghosts.'
I first guided them to their lodgings and put the box into my inventory. In this era, Japan was going through a period of significant economic change, so holding too much cash could cause its value to drop instantly. I planned to exchange it for gold or buy land later.
From the next day, I bought the sisters underwear, comfortable Western clothes, daily necessities, writing tools and notebooks for studying, and the dolls and toys they wanted. I also ordered furniture for them. Their expressions didn't change, so I couldn't tell if they liked them or not.
After returning, I asked the sisters various things to see how much knowledge they had. Whether it was because the sisters were naturally smart or because of their family's education, despite their young age, they possessed knowledge beyond the high school level of this era.
'Hmm... There's nothing in particular I need to teach them.'
But there was a problem. Now that Nezuko was also receiving inpatients, the hospital rooms were a bit cramped. So I purchased a large house next to the clinic and began construction, turning it into a Western-style building. I planned to move the entire living quarters there. Of course, I designed it myself.
Then I called Muichiro and Sanemi and first assessed their skills.
Clang! Clang! Clang!
"This is enough."
When I gave the stop signal, Muichiro and Sanemi collapsed on the ground.
"Huff, huff, huff... This monster of a human..." Sanemi said, looking at me with ragged breath. Muichiro agreed, "How can the two of us attack you and you not even break a sweat?"
"No adult breaks a sweat playing with babies for a bit."
At my words, they couldn't retort and just lay on the ground resting.
"Damn it..."
I let them rest enough, then explained the problems with Muichiro's swordsmanship.
"You often momentarily disappear from the opponent's sight or conceal your swordsmanship to make your attacks unpredictable. It's incredibly childish, so stop it. I'll show you something interesting."
I took a cloth from my pocket, covered my eyes, and said to Muichiro, "Attack me again."
At that, Muichiro hesitated for a moment, then drew his sword and began attacking.
Clang! Clang! Clang!
Naturally, Muichiro's attacks didn't work at all. He seemed quite surprised.
"How can you do that with your eyes covered?"
I removed the cloth, put it back in my pocket, and said, "Swordsmen who have reached a certain level don't need to rely on their eyesight. Up until now, you've been lucky enough to face only weaklings, so those cheap tricks worked. If that wasn't the case, you might not even be here now."
I briefly explained the state of 'The Transparent World' to them.
"I see..."
"That's not to say Mist Breathing is garbage. Considering that Mist Breathing's techniques are a form of swordsmanship that piles short consecutive strikes. Rather than the opponent's vision, it would be better to focus on how to utilize the variations in the swordsmanship itself and your own speed."
This time I looked at Sanemi. This guy really seemed to need mental training. His murderous intent was too thick, and I could see him wasting energy unnecessarily.
"I told you to tone down your personality. Is 'keep your head cool and your heart hot' really that difficult?"
I called over Hinaki and Nichika, who had been playing nearby.
"Give this guy a thorough education in manners."
"Yes, understood, Sword Saint."
At that, Sanemi looked dumbfounded. "What??? Wait a minute! I came here to learn swordsmanship, not manners!"
"Shut up and do it. Swordsmanship comes after. If you fail this, I'll send you to a temple to meditate for a whole month, so deal with it!"
From the next day, while consulting with patients and sparring with Muichiro, correcting his bad habits, I watched over Sanemi's etiquette education. After about two weeks, Muichiro's bad habits were gradually corrected, and perhaps due to the etiquette education, Sanemi's murderous intent had also lessened to some extent.
"Hmm... You've improved."
From that day, I had Sanemi join the sparring as well, refining his swordsmanship. Certainly, Muichiro was a talented guy. Old habits are hard to break, but he quickly started correcting his reliance on the opponent's vision to instead using the variations in the swordsmanship itself and his fast footwork. Sanemi's swordsmanship was also visibly losing its murderous intent and beginning to stabilize.
"Remarkable progress. Sanemi, engrave this well in your mind…"
"I know! Keep your head cool and your heart hot."
Now that he could feel his own swordsmanship changing, he understood what I said. Muichiro created a new form on his own—a unique form that gave the impression that multiple enemies were striking simultaneously, using his fast footwork.
It had already been a month since they arrived. Sanemi and Muichiro packed their bags and left the clinic. After they left, it was truly quiet for a while. Occasionally, I could only hear the voices of the Ubuyashiki sisters playing outside and the chatter of patients.
'Peaceful.'
Then one day, a crow came and delivered a message. Inside was a request to make more slingshots, as the ones I had made for Tengen's wives had been very effective. It seemed that since items made of carbon fiber were physically impossible to produce in this era, and they couldn't replicate them, they were asking me to make more.
I gave the crow some food and said, "Tell them I understand."
Caw~!
Two months passed like that, and the building next to the clinic was completed. All the clinic's residents moved there. Now, the clinic would be used purely as a clinic, and the building next door as their home. The rooms were very spacious, which Nezuko loved, and the Ubuyashiki sisters, though expressionless, seemed to like it quite well.
After the move was finished, I called Nezuko and the sisters and spoke to them.
"We'll stop by your respective homes in a week, so think of gifts for your families. Nezuko, post this information on the clinic bulletin board."
"Okay, I'll prepare right away."
Nezuko was very excited. It had been a while since she'd seen her family, thanks to the Hashira, and she must have missed them a lot. The sisters remained expressionless.
I gave the nurses time off, then took Nezuko and the sisters to the city, bought a large number of gifts for their families, loaded them into the car, and set off. On the way, I peeled boiled eggs and ate snacks, making it feel like a trip. Nezuko and the sisters in the back seat also seemed to have a great time.
Finally, we arrived at Tanjiro's house. For some reason, Tanjiro was home today and came out to greet us warmly.
"Nezuko~! Welcome home! I missed you!"
Tanjiro hugged Nezuko tightly.
"Teacher, have you been well? It's good to see you. But who are these children..."
Tanjiro looked at the Ubuyashiki sisters and asked.
"They're my new assistants."
"Ah~ I see. Please, come inside."
Tanjiro's house itself was unchanged, but interestingly, the number of chickens had increased again. They had even expanded the chicken coop. It seemed this mountain might be blessed by a god of fertility.
Anyway, as we entered the house, Tanjiro's family welcomed us warmly. Tanjuro and Kie were also healthy and well.
"Wow~ Big sis! I missed you!!"
"Nezuko, welcome home."
"Teacher, it's been a long time."
The Tanjiro family's circumstances had improved greatly. The children's clothes looked nice, various parts of the house had been repaired neatly, and they had many books for the children to study.
Nezuko distributed the gifts she had brought to her younger siblings.
"Wow~ Thank you, big sis! The sweets you buy are the best!"
Nezuko beamed at her siblings' happiness. She then told her family that she had become a doctor.
"Wow~ Really? So big sis is a doctor now?"
"Of course. If you ever get sick, tell me. I'll cure you."
"Okay! I will, big sis."
At that, Kie shed tears and thanked me.
"Teacher, thank you for teaching Nezuko so well."
"Not at all. It's thanks to Nezuko's hard work."
But then the Ubuyashiki sisters, watching this scene, suddenly started crying for no apparent reason.
"Hmm? Why are you crying?"
"We were just wondering what it would have been like if our family had been like this..."
The Ubuyashiki family was quite strict in raising their children, so this warm, happy family scene must have been enviable to the sisters. Thinking that, I felt a little sorry for them, so I gave them a brief hug and patted their heads.
"Are you sad? Then play with us. We know some fun games."
Seeing the sisters crying, Nezuko's younger siblings came over, took their hands, and tried to lead them outside.
"Wait! Sword Saint!"
The sisters, flustered, called out to me, but I gestured for them to go out and play. The children played in front of the house and only returned around evening. They had dirt all over them, so it seemed they had been running around having fun. The sisters immediately apologized to me for getting their clothes dirty.
"We're sorry, Sword Saint. We'll go wash and do laundry right away…"
"No, it's fine. More importantly, did you have fun?"
"Huh? Ah... yes..."
At my question, the Ubuyashiki sisters, looking embarrassed, answered that way. They were still children, after all.
We stayed at Tanjiro's house for three days and then prepared to leave. During that time, the sisters also ran around playing with Tanjiro's younger siblings. I noticed that their expressions were slowly becoming more animated, so it seemed that bringing them here had a positive effect on them.
"Um, Teacher. Could I possibly get some more of those stretchy contraceptive devices?"
Just as we were about to leave, Tanjuro asked me for more condoms.
"Excuse me? I gave you over a thousand last time... Was that not enough?"
"Yes..."
At my words, Tanjuro, very embarrassed, said yes. This couple had used up over a thousand in just over a year.
"W-Well... okay, I understand."
I had a lot I could have said, but I just held back and handed him two thousand this time.
"Thank you, Teacher."