Teru was dizzy and pale as he leaned on the seat. People around him looked concerned, and were ready to call the attendants for help.

Teru’s heartbeat and breathing returned to normal. He took a deep breath with ease, and stopped them and smiled, saying, "I haven't got used to taking the train. It was my first time. It's fine."

The carriage fell back into silence.

But of course, that wasn't the real reason for his discomfort. As a brilliant doctor, Teru understood his body well. Due to his wife's nocturnal habits, he had not maintained a regular sleep schedule for over a year. Despite having sufficient sleep and a strong physique, he couldn't defy the natural order of day and night. His body's functions were disrupted, making it difficult for him to handle intense physical activity or even use breathing techniques. Otherwise, defeating the swordsman earlier would have been much easier.

But why was that swordsman following me?

Teru began to ponder, but he couldn't recall if he had any enemies.

He sensed Kokushimou's gaze, but the emotion conveyed was more indifference than hostility.

Anyway. I'll just avoid him after we get off the train.

Just as Teru was thinking of it, the observing presence on the roof of the train suddenly disappeared, and even when he arrived at the ancestral home of the Murasame family, there was no sign of the swordsman.

The Murasame family, namely the family with wisteria family crest, recognized by the Demon Slayer Corps for their past aid, offered free hospitality to every member of the Corps. However, this had nothing to do with Teru's visit this time. He was here to participate in the meeting organized by the Murasame family for exceptional doctors. These regular meetings helped maintain their influence and connections with various fields in society.

Standing at the entrance of the house, to be more exact, one of the interconnected houses, Teru lightly knocked on the door and waited for someone to answer.

"Is this Dr. Watanabe? The meeting starts tomorrow; please rest for today. Your room is ready, Please follow me." a servant said, bowing to Teru.

After taking a bath, Teru sat on the tatami floor. In winter the daytime was short, and it had become dark outside. Suppressing his drowsiness, he went over what he had planned to do at the meeting.

Firstly, he wanted to inquire about specific medical instruments. Based on Muzan's condition, it seemed to be a light-sensitive skin disease, but there were too many types, and misdiagnosis could lead to severe results. It was crucial to have the right medical equipment. He also wanted to consult other doctors on how to distinguish between different skin diseases. Furthermore, regardless of the illness, there were a few medicinal herbs that could be used universally, so he needed to collect information on them as well.

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Rubbing his dark eye circles, Teru sighed, but soon he felt energized and motivated again. All the hard work was worth it if it meant curing his wife's illness and allowing her to see the sun again and feel its warmth!

Knock, knock, knock!

A slow and deliberate knock came from outside the door.

Teru opened the door. On seeing the man standing outside, he was ready to draw his sword from the system space at any moment.

Outside the door was Kokushibou. He gave him a letter and spoke, each word with a pause, "Muzan...sama... letter."

As Teru opened the letter to read its contents, it was short, only a few lines.

"Teru, one of my subordinates happens to be on duty at Spider Mountain. You can get close to him and ask for any help you need. He doesn't talk much, but he's reliable, and his swordsmanship is exceptional."

Kokushibou stood at the door, his expression indifferent.

Today, while executing a mission on the train, he suddenly came across a door underfoot and was transported to the Infinity Castle. Muzan-sama put her eyes on him, and ordered in her mind: "Kokushibou, go protect Teru Watanabe closely and pay attention to the situation around him, especially any other wome...humans. Report back to me in letters."

Kokushibou was a bit puzzled. Was this for the purpose of eliminating the Demon Slayer Corps, or was it just a whim of Muzan-sama?

After reading the letter, Teru felt relieved and relaxed.

So, this powerful swordsman is a bodyguard arranged by his wife to ensure his safety?

He felt a little guilty; he had damaged the man's clothes and even wounded his arm. He should find some time to make up for him.

"Welcome, welcome! There are two beds available!"

Teru realized that he still didn't know the swordsman's name. "What's your name?"

"Kokushi...," Kokushibou recalled Muzan-sama's instructions, deciding it was better not to use the name as a demon in front of this man.

"Tsugikuni, Michikatsu." Kokushibou said.

"Great name!" Teru exclaimed.

Kokushibou nodded.

Not long after, the oil lamp burnt out. As a demon, Kokushibou didn't need to sleep, but to avoid arousing suspicion, he still laid on the bed.

"Muzan praised you. She said the company only has six competent subordinates, and you are the most reliable among them."

Kokushibou recalled his colleagues one after another, silently acknowledging and feeling a subtle sense of pride.

"Your birthmark on your face is so cool, it looks like four closed eyes. Is it natural?"

Kokushibou didn't pay attention to his words; he just quietly pondered how long it had been since he last slept.

Was it since the moment he cut off his brother's body? Or was it when he became a demon?

No, it started even earlier, right? When he abandoned his wife and children and joined the Demon Slayer Corps.

The sound of a flute reached his ears.

"How was it? Not bad, huh? I didn't like playing the flute before; it's a legacy from my parents. They say my father and mother fell in love because of the flute." Teru said with a smile.

"Good," Brief replies as always.

Kokushibou touched the flute that was broken in half, hidden against his chest. With his demon abilities, he temporarily connected the broken parts and started playing it.

At the end of the piece, he felt a sense of tranquility. He had barely had this feeling for hundreds of years.

Teru stopped talking; he had fallen asleep.

That was the flute he personally gave to his younger brother, also the flute he cut in half together with his brother’s body.

Yoriichi Tsugikuni...his brother’s name. A good name. A name better than his own.

Kokushibou closed his eyes and, for once, allowed himself to fall asleep.

He dreamed of Yoriichi.