Before leaving, I said to Tanjiro and Zenitsu, who had come to see me off.
"Tanjiro, Zenitsu, listen carefully. In Total Concentration Breathing, there is something called 'Total Concentration Constant'."
This was originally something Shinobu would teach them, but since she was leaving with me for research, I needed to tell them.
"What is Total Concentration Constant?"
"Right now, you only use breathing when performing techniques, don't you?"
"Yes..."
"It means doing that breathing in your daily life, even while sleeping."
At that, Zenitsu asked, flustered, "Huh?? Is that possible?"
"Yes, it's possible. If you achieve Total Concentration Constant, your basic physical strength and breathing proficiency will increase. For your information, the Hashira and some other members are already doing it."
"I see..."
"I'll talk to the Demon Slayer Corps. They'll give you some time until Inosuke recovers from his injuries. Make sure you master Total Concentration Constant by then. And teach Inosuke as well."
At that, Tanjiro answered loudly, "Yes, Teacher!"
But Zenitsu looked like he was about to cry at the prospect of more training.
"More training..."
Shinobu also told the Butterfly Mansion residents to help Tanjiro and the others with their training.
"Okay. We'll help as much as we can."
After that, Shinobu had a Kasugai Crow inform the Demon Slayer Corps on my behalf, buying Tanjiro and the others some time.
"Thank you."
"Not at all."
"Let's go."
We said goodbye to Tanjiro, Zenitsu, and the Butterfly Mansion residents, got in the car, and departed for the clinic. On the way, I slowly told Shinobu about Tanjiro's family and about Tamayo.
"What??? You're researching together with a demon, even if she holds a grudge against Muzan? Does the Master know about this?"
As expected, Shinobu couldn't accept it easily.
"Yes, he knows. I told him."
"Still..."
"And Tamayo has been researching for centuries to capture Muzan. She's broken free of Muzan's control and no longer eats humans."
"But she's still a demon. You can't trust demons."
"Of course, as you say, most demons can't be trusted. But some became demons unintentionally. Like Tanjiro's sister, and Tamayo. And now Muzan is creating demons indiscriminately, so those victims will only increase. What sin have those forcibly turned into demons committed?"
"That's true, but..."
"Capturing Muzan is important, but I think we also need to find a way to treat those people when they're turned. So I'll give you some time. Think about it. If you decide you absolutely can't work with a demon, let me know. I'll take you back to the Butterfly Mansion."
Shinobu was silent, thinking with a serious expression. Then she asked the Ubuyashiki sisters, who were sitting nearby.
"Did you two know about this?"
At her question, the eldest daughter, Hinaki, answered, "Yes. At first, we didn't like it either because she's a demon. But Hanako, Tanjiro's sister, has never eaten a human. She's just a cute younger sister who sleeps a lot. And we think Tamayo is also a very kind and good person."
Then the second daughter continued, "I also want to treat people like Hanako and Tamayo, who became demons unintentionally, if we can."
When even the Ubuyashiki children, who had the deepest grudges, said that, Shinobu's expression softened slightly. She sighed, looked out the window, and continued to think.
We ate snacks, drinks, and boiled eggs as we traveled, eventually arriving at the clinic. The sisters and I began unloading the luggage from the car, but Shinobu, still thinking, remained in the car. I asked her, "Your luggage is the only thing left. What do you want to do? Should I take you back to the Butterfly Mansion?"
"Hoo... Fine. I'll join the research too."
Finally, Shinobu seemed to have made up her mind. I assigned her a room, had her unpack, and then introduced her to Tamayo. Tamayo and Shinobu sat in the living room and began talking.
"You must hold a grudge against demons. Thank you for making such a difficult decision."
Tamayo, having heard Shinobu's story, spoke with sympathy.
"Not at all. Anyway, I look forward to working with you."
"The feeling is mutual."
Seeing that the conversation was over, I handed Tamayo the blood I had obtained from Rui.
"This is the Lower Moon's blood I obtained this time. And the Demon Slayer Corps has agreed to help supply demon blood from now on."
"I see. I'm glad things worked out well."
Tamayo took the blood and went to the lab with Shinobu, where she shared her research data. Shinobu was amazed at Tamoyo's research.
"I didn't know you had progressed this far. It's incredible!"
"Not at all. It's thanks to Teacher Jin's active support."
I had thought it might take time for them to become close, but fortunately, as fellow pharmacology researchers, they seemed to get along well and would likely become close quickly.
That evening, after introducing Shinobu to the Tanjiro family, I prepared a delicious meal and held a modest welcome party. Nezuko, who was close with Shinobu, was delighted that she would be staying for a while.
"What? So you and the Sword Saint are married?"
"Yes, that's right."
Shinobu seemed very surprised that I had married Nezuko.
"Congratulations... I've been nothing but surprised since I came here."
After the welcome party ended, I gave the family Tanjiro's letters.
The next day, I took a day off from the clinic and went into town with Shinobu to purchase necessary furniture, daily necessities, and supplies for the research.
"Thank you for today."
"Don't mention it. Someone who knows the area had to help."
After a moment's hesitation, Shinobu said to me, "Seeing Hanako and Tamayo, I wonder if I've been too consumed by my grudge. They both seem like good people."
"I'm glad you think so."
Shinobu seemed to have sorted out her feelings. With Tamayo and Shinobu working together, I thought the medicine to turn demons back into humans and the medicine to weaken Muzan would be completed soon.
'Is everything roughly settled?'
Muzan had switched to a war of attrition, causing more civilian casualties, but I had also strengthened the Demon Slayer Corps Hashira, and the medicine seemed to be progressing without issue. So if we only resolved the current incidents, everything should go smoothly.
Click
"I'm home!"
While I was helping organize Shinobu's things and sitting in the room thinking about this and that, Nezuko finished her clinic work and came home.
"You worked hard today. Good job. Starting tomorrow, I'll be taking consultations again, so it should be easier."
"I'm used to it now, so it's not that hard."
"Really? That's good."
Nezuko hesitated for a moment, then made a request.
"Um, while you were away, some poor people came and asked for help. It seems there are people who can't come because they can't afford the medical fees."
"Come to think of it, there is a slum not far from here."
"So, I was thinking, maybe we could go and help them on weekends sometimes..."
Nezuko, knowing I was busy, seemed hesitant to ask. Seeing this, Nezuko was certainly kind.
"Hmm... It's certainly a good thing. But with Hanako's matter and the demons' movements being unstable, and since I'm not just a doctor, I don't have time. Unfortunately, I don't have time to care for them. And I can't let you go alone. If the demons find out we're married and target you, the whole family could be in danger."
When I refused, citing realistic problems, Nezuko looked quite dejected.
"I see..."
She probably knew I was right, but seeing her like that made it difficult to watch.
"Ahem... Instead, we could see them briefly at the clinic on weekends."
At that, Nezuko brightened immediately.
"Wow~ Really? Thank you!"
"As long as we don't overdo it."
"Okay. Ah, by the way! Today, the clinic received doctor licenses from the government. For both of us. They're licenses given to people who have properly studied Western medicine. It seems the government is creating something like a medical association to manage things systematically."
Certainly, this was around the time the medical association was being formed in Japan. But it was still an era of superstition, with many practicing quack medicine, and many still valued traditional Japanese medicine over Western medicine.
"Hmm... I see."
"Huh? You don't look happy. Now we're official government doctors..."
"No, I'm happy."
I said that, but there was a reason I didn't like it. When Nezuko grew older and World War II broke out, being a doctor wouldn't be such a good profession. The government might requisition them and send them here and there.
'I wonder what the Demon Slayer Corps would think if they survived long and realized that people in other countries see them as demons.'
And so, from the next day, I resumed consultations. On weekend mornings, as promised, Nezuko and I treated the people in the slums. But it wasn't completely free. We treated them at a reduced rate, and those with no money were asked to help at the clinic or pay in goods.
I could have done it for free, but I knew that would cause various problems. Especially with slum residents. They had to work harder than others just to survive, so relying on others wasn't good. I had made sure Nezuko understood this as well.
'Now it's time to move on.'
The medicine research seemed to be progressing without issue, and I had now mastered all the Total Concentration Breathing techniques. So it was time to prepare to return to the Naruto world. I wanted to obtain Nakime's Blood Demon Art, the Infinity Castle, but if I acquired it now, Muzan might feel threatened and cause havoc or flee overseas. So I would need to deal with Muzan at the same time, but that would lead to an immediate ending, and I wouldn't be able to enjoy the story fully.
'Really... I have to understand the villain boss's circumstances just to enjoy the game...'
The Infinity Castle was certainly a good ability. It had many functions like manipulating the interior, spatial movement, forced summoning, and could even be used as an inventory where time flows. In short, it meant acquiring another dimension. So even if I couldn't obtain anything else from Demon Slayer, I had to obtain the Infinity Castle.
'I'll continue Naruto while finishing Demon Slayer and obtaining the Infinity Castle.'
With that plan in mind, I ended Demon Slayer.
[Exiting the Demon Slayer world.]
[Settling rewards.]
[Kamado Nezuko bond level 8]
[Kocho Shinobu bond level 8]
[Kamado Tanjiro bond level 7]
[Ubuyashiki Hinaki bond level 7]
[Ubuyashiki Nichika bond level 7]
[Kamado Tanjuro bond level 7]
[Kamado Kie bond level 7]
[Kamado Takeo bond level 6]
[Kamado Hanako bond level 6]
[Kamado Rokuta bond level 6]
[Ubuyashiki Kagaya bond level 6]
[Iguro Obanai bond level 6]
[Kanroji Mitsuri bond level 6]
[Himejima Gyomei bond level 6]
[Tamayo bond level 6]
[Rengoku Kyojuro bond level 5]
[Uzui Tengen bond level 5]
[Tokito Muichiro bond level 5]
[Tomioka Giyu bond level 5]
[Kuwajima Jigoro bond level 5]
[Shinazugawa Sanemi bond level 5]
[Ubuyashiki Kiriya bond level 4]
[Ubuyashiki Kanata bond level 4]
[Ubuyashiki Kuina bond level 4]
[Agatsuma Zenitsu bond level 4]
[Ubuyashiki Amane bond level 3]
[Yushiro bond level 3]
[Kibutsuji Muzan bond level 3]
[Hashibara Inosuke bond level 2]
[Chachamaru bond level 2]
[...]
[...]
[You have acquired 40,750 points as a reward for progressing in Demon Slayer.]
Even without progressing the story much, I received quite a few points. Probably because I had captured Kokushibo and the Hashira had grown stronger, leading to the capture of Upper and Lower Moons.
'Shinobu's bond level is odd again...'
Bond levels not only give information about approximate points but also indicate affection for the person. Seeing that Shinobu's bond level was similar to Nezuko's, with whom I was married, it seemed Shinobu also had feelings for me.
'So that's why she reacted so shockingly to hearing I married Nezuko?'
I liked being popular with women. But I also had to be prepared for the headaches that would come with it. Fortunately, things had worked out well in One Piece, Konosuba, and Fate, but women generally weren't so generous. For example, if I got involved with multiple women in Marvel, Natasha would definitely try to kill me. This was why I hesitated to use the [Companion Entry Ticket].
Anyway, I decided to worry about that when I was in that world. Looking around, I saw that I wasn't back in reality but in my house in the Naruto world. Probably because I had paused Naruto to go to Demon Slayer.
"It's nice to be back home after so long."