"Hmm?"

Muzan sat in the room, frowning.

She could sense that the countermove she had set up just in case, the complex of two demons, a monster capable of conquering a town by itself, had been killed.

Not only was it killed, but she could feel through her cells that it was killed with just one strike.

"The hashira of the Demon Slayer Corps, huh? Annoying..." Muzan's eyes flashed with a trace of anger.

No one else other than a hashira have such strength.

"Why hasn't he come back yet?" Muzan frowned and looked at the door, but there was still no movement. For some reason, she felt even more disdain for the Demon Slayer Corps.

"Sooner or later, I'll kill them all!"

...

In general, the huge sound would have caused one's eardrums to burst, but Tanjiro felt that the dragon roar was surprisingly gentle.

He gradually opened his eyes and saw a gigantic demon that seemed to have been torn apart and killed in an instant.

Standing before the demon, under the moonlit night, was a man wearing with a red demon mask on his face, his sword slowly put into the scabbard.

"Hey, young man, you look pretty spirited," Teru turned his head and said, smiling. His voice was filled with care that put Tanjiro at ease.

Tanjiro was covered in blood, with a tired expression on his face, and for some reason, Teru made this evaluation.

"Um..." Tanjiro was taken aback but quickly spoke, "Thank you for helping me and my sister Nezuko..."

"No need for thanks. " Teru casually stroked his chin.

Tanjiro could sense that Teru wasn’t a dangerous person, but instead emitted a comforting and sunny vibe, which made him feel relaxed. He smiled and continued, "Thank you."

He wondered why this mister chose to wear a mask that resembled a demon's face. It might cause confusion among the Demon Slayers Corps and even lead to direct attacks.

"Oh, by the way, this is my sister. Although she is a demon, she will never hurt anyone..." Tanjiro quickly introduced his sister standing behind him.

In the Demon Slayer Corps, protecting demons was strictly prohibited, but Tanjiro didn’t think the man who just saved their lives would hurt his sister.

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"It seems you can't hide demons in your Corps, huh? Such a rigid place!" Teru remarked.

"Yes..." Tanjiro nodded, confirming Teru's question, and then he looked at Teru with curiosity.

"But, mister, you're a member of the Demon Slayer Corps, right?"

"No, I never said I was a member of your Corps." Teru decisively shook his head.

"But you know about a breathing technique!" Tanjiro said excitedly.

"That's because the system transformed my swordsmanship like this. I didn't want it to be this way, but it seems to have added some special effects and sound effects, so it’s fine..." Teru mumbled some words that Tanjiro didn't understand.

Dragon breathing, he had never heard of it before. It must be some obscure breathing technique. Tanjiro thought to himself.

Unique breathing techniques often disappeared after a few generations, making it difficult for later generations to learn them.

However, he would never have guessed that Teru was the only person in the world using this breathing technique.

"By the way, what's your name?" Tanjiro asked.

"I prefer mysticism, young man. Your words make me uneasy," Teru replied with an unfazed tone.

"Just call me 'Mr. Demon.'"

"In any case, you are a promising young man. Hope you stay alive. Didn't expect this world to be so dangerous." Teru sighed.

Tanjiro thought that it was others who would find Teru dangerous.

He couldn't forget how Teru had easily killed that terrifying monster just now; faced with it, he couldn’t even move.

"Well... my sister and I will definitely survive," Tanjiro said, looking at his sister behind him.

"So we have some kind of connection, huh? You with your demon sister, and me with this demon mask. It’s like the beginning of a legend." Teru smiled.

"I'm not someone who can become a legend though..." Tanjiro quickly denied.

"So, shall we meet again some other time?" Teru stood up and said, "My wife is waiting for me, and if I don't go back for so long, she might get angry."

"And the other two inside, I won't disturb you in the middle of the night," Teru shouted into the room. There was no reply.

Teru carelessly swung his sword as he walked back, not afraid of encountering demons or vampires at night; after all, these things were weak.

Tanjiro bowed to express his gratitude again. He touched his tired sister who had fallen asleep, and chuckled.

"Didn't expect that Mr. Demon has a wife. He seems to be carefree, but actually he is quite reliable. I can sense that. His wife must be a serious woman."

...

As the reward for the battle just taking place, the system gave him a sword that would never break, a haori that could conceal his presence, and the ability to see through the enemy's intentions. Teru checked them on his way home. He stepped into the house.

"Sorry, sorry. I met a black cat on the way and got lost for a while," Teru quickly apologized after returning home, but in his tone of speech there was no sense of remorse.

Muzan glanced at him with her crimson eyes and returned to reading her book.

"By the way, I have a gift for you." Teru took out the red demon mask. "What do you think?"

Muzan glanced at it dismissively, "Do you think I need such childish toys?"

Teru put it on his face, his voice muffled, "Then I think I do."

He walked to the window, suddenly sensing a strong aura. He turned his head sharply, only to see a purple sleeve and hilt disappear around the corner.

"This world is truly dangerous. So many powerful people emerge in just one day. And that person just now, he looked like he came from the Warring States period. Do even the most powerful swordsman have a hobby for cosplay?" Teru wondered.

"I plan to go to the family near Mount Natagumo to study medical arts in a few days. Would you like to come along? Their flower tea is delicious. It's so enjoyable to drink it while basking in the sun. Shall we hang wisteria all over our house?"

Muzan glanced at him, clearly a warning: don't bring back those wisteria!

Teru shrugged. Afte all, wisteria are so beautiful.