He hadn't slept well at all the previous night.

After all, he had just slept for 20 full hours earlier. Asking him to continue sleeping was really too difficult for him.  

It wasn't until around 3 or 4 AM that he finally fell asleep again.  

Unfortunately, before he could sleep for long, the sky was already bright.  

In order to reset his circadian rhythm, he still forced himself out of bed, wandering around to dispel the lingering sleepiness.  

It had to be said, the Butterfly Mansion environment really was excellent. Flowers and greenery were planted everywhere. Occasionally, there were even butterflies fluttering before his eyes.  

He took a deep breath. The scent of wisterias cleared his weary mind a bit.  

"That's right, I can open the chest now!"  

He opened the system and unhesitatingly opened the chest.  

Yet another repetitive and rousing tune!  

He rubbed his hands excitedly. The first time he had drawn the demon blade Senjin. The second time he had gotten an Impurity Cleansing Potion.  

He wondered what good thing he would get this time.  

Accompanying the end of the music, the chest heavily crashed to the ground.  

A dazzling ray of light flashed as he narrowed his eyes, but his gaze never left the chest.  

As the chest opened, the item inside also slowly rose up.  

His eyes gradually widened as he saw a small silver colored toy whistle float from the system space and appear in his hand.  

It didn't look like a normal whistle, with its head turned in a different way as many dragon-like patterns ran along its body.

"A whistle? What am I going to do with this?" he wondered. "System, tell me its function."  

[System suggests that host figure it out himself]

After that, no matter how many times he called after that, the system didn't respond at all.  

Just as he was pondering whether he should just try using it, Shinobu happened to pass by from the side.  

"Good morning." She walked over, greeting him while brushing her hair.  

"Good morning." He returned the greeting similarly, while also trying to hide the silver whistle behind his back.  

But unfortunately, Shinobu had already noticed.  

"What's that?" She pointed at his hand and asked again.  

"....Just a useless toy, you don't need to worry about it." He said.   

"I could hear your hands clenching around something. Why don't you show it to me?" She asked once more.  

Sighing, he put forward his hands, revealing a shining silver whistle which didn't look like a whistle at all.  

Shinobu's eyes glowed. 'Is that...a whistle...perhaps a strange one... Why is every item he has so strange?' she wondered.

"Can I touch it?" She asked, curiosity visible in her eyes.  

"Miss Shinobu, this whistle has a lot of importance in my family. I'm afraid I cannot let you touch it." He said with a sincere expression.  

He didn't even know what the whistle actually does, so it was better if he did not let Shinobu examine it before he knew about its uses.  

Seeing his eyes, Shinobu did not pry further. She turned around and looked at the training area.  

He quickly put the whistle in his pocket and started changing the topic. "Miss Shinobu, you said you'd start teaching me the breathing techniques today!"  

"That eager?" Shinobu was a bit surprised, then smiled. "Alright, let me first tell you some basics about the breathing techniques."  

The so-called basics described the original breath styles, derived styles, the various factions of existing breaths, and the traits of each breath.  

These were all things he already knew. What truly interested him were some interesting rumors and learning experiences Shinobu talked about and things not mentioned in the original work.  

So he listened very attentively, feeling it was quite interesting. This went on for an hour.  

"Ah, sorry! Seems like I was explaining too much!" Realizing her stories had gradually deviated from the breathing techniques, Shinobu hurriedly stopped herself.  

How careless...she couldn't help but knock her own forehead.  

He didn't mind, only asking. "If I'm going to learn breathing techniques, will I be studying the Water Breathing?"  

The Water Breathing had high versatility. It was the easiest to learn and also the most widely used breathing style.  

Shinobu also knew this. After all, she had first learned the water breathing until later developing her own breathing style.  

She thought for a bit, then suddenly said, "How about you learn the Insect Breathing instead?"  

The Insect Breathing?!  

He was stunned.  

The Insect Breathing had a speed and piercing focused style. It was a completely new breathing technique Shinobu had developed based on her weak strength and slender, nimble physique.  

How could it be suitable for him to learn?  

"I'm most proficient with the Insect Breathing," Shinobu quickly explained. "As for the Water Breathing, I'm actually not that skilled with it. Of course you can try it first. If it really doesn't work, you can learn other breathing styles. After all, I'm nurturing you as a student. It wouldn't be right not to teach you the Insect Breathing."  

He contemplated for a bit and nodded.  

"Fine!"   

In the end, he was planning to find Tanjirou and learn the Sun Breathing anyway. Using the Insect Breathing as a transition was also okay.  

Seeing him agree, Shinobu also started teaching him how to use the insect breathing.  

Under her patient guidance, Kenshi gradually grasped the basics.

After a while, seeing him steadily breathing, Shinobu was a bit surprised. She had only given a few pointers, yet he grasped it so quickly.  

To verify her guess, she placed her hand on his chest.  

Kenshi, who was practicing, suddenly felt a warm hand on his chest. This directly broke his concentration!   

"Cough cough cough! What's wrong?" He looked at the little hand on his chest, somewhat confused.

But Shinobu didn't even lift her head, just saying, "Don't stop, keep going!"  

Looking at her very serious face, he closed his eyes then continued the breathing from before.  

Very soon, he felt pressure in his lungs, but with the help of the breathing technique, his perception of the surroundings became more sensitive.  

He knew he could grasp it so quickly because of the Impurity Cleansing Potion from the system.  And from Shinobu's surprised expression, he could tell his performance must be very good!  

As expected of system products, guaranteed quality!  

Before long, the pressure in his lungs finally reached the limit. With Kenshi suddenly coughing, the Insect Breathing stopped.  

Shinobu also withdrew her hand, looking at him somewhat complexly. His talent exceeded her imagination. Keeping him here would be too wasteful of his gifts.  

What to do?  

Should she recommend him to other Hashiras?  

Shinobu was a bit hesitant. On the other side, Kenshi looked at her excitedly, asking. "How was it? Was I okay?"  

She paused, just about to say something, when Aoi suddenly walked over from not far away, greeting them.   

"Lady Shinobu, Mr. Kenshi, it's time to eat."  

Shinobu tidied up and controlled her emotions, revealing her signature smile again. "Let's go eat first! It looks like someone can hardly wait!"  

...  

After a pleasant breakfast, Kenshi continued following Shinobu to practice the Insect Breathing.  

But he also discovered no matter how long he trained, he could only maintain the Insect Breathing for a certain period before his lungs couldn't take it anymore.  

Shinobu, who was watching him, immediately identified the issue.   

"Your current physical fitness is too poor," she explained. "Breathing techniques ultimately still rely on the human body. The higher one's physique, the longer they can maintain the breathing techniques, and the greater the boost gained from them. The two complement each other."  

"So in other words...I need physical training?"  

She nodded. "Correct, but there's no rush for now. Your wounds haven't healed yet. Forcing yourself will only leave hidden wounds. Wait a few more days! I'll also prepare a training plan for you during this time."  

"I understand."  

After that, Shinobu explained to him the traits and precautions of the Insect Breathing, including the four forms she created herself:  

Insect Breathing - Butterfly Dance: Caprice   

Moving like a fluttering butterfly while using lighter force to instantly pierce five times, slicing open the demon's skin. Combined with Shinobu's poison blades, it brings about their toxic deaths.  

Insect Breathing - Dance of the Bee Sting: True Flutter   

Fiercely stabbing forward with a thin blade coated in toxins. Due to the instantaneous explosive power, the force is enough to pierce through a demon's skull.   

Insect Breathing - Dragonfly Dance: Compound Eye Hexagon  

A six-hit technique injecting massive amounts of poison into the opponent's body. Killing with the sharp and quick stabs of a blade transformed into toxic needles.   

Insect Breathing - Dance of the Centipede: Hundred-Legged Zigzag   

Through forceful stomping that can uplift the very ground, zigzagging in all directions, confusing the opponent, then striking with the blade when there's an opening.  

Of course, now Kenshi could only listen and get a general impression. Actual training would have to wait until he recovered.  

After all, Shinobu was a Hashira. She was very busy with work and couldn't constantly instruct him.  

So in the following days, he could only repeatedly practice the breathing techniques. Through perseverant efforts, his breathing techniques became increasingly refined and skilled, even the duration he could maintain them saw gradual increase.  

This made him very happy, constantly praising the Cleansing Potion that made this a bit easy for him.  If not for that potion, he wouldn't have such astounding talent either.  

Shinobu was also very happy. Not only was Kenshi gifted, he was also hardworking. 

At the same time during this period, Kenshi also researched the demon blade Senjin.  

In the desolate area inside the sword, he tentatively used the arm extended by his consciousness to touch the evil spirit floating in midair. Almost instantly, the demon blade Senjin lit up with a blue-purple glow.  

And in that instant, he could also feel the existence of every fragment in the sword.  However, the evil spirit didn't even show any visible movements.

After trying a few more times, he understood that as long as he established a connection with the evil spirit, he could rely on it to control all of the blade fragments.   

After that, he tentatively conveyed his intent, asking it to allow him to use the sword. However, even after an hour, he couldn't feel anything other than the first time when the evil spirit opened its eye. He never saw it move again.   

On his 157th attempt, he shouted out loud, "You damn sword! Let me control you, or at least talk to me and tell me what you want. I can't stand looking at the statue-like evil spirit anymore!"  

Kekeke  

Just as he said those words, he suddenly heard an eerie laughter. The next moment, the sword suddenly became extremely sturdy, no longer having that shattering feeling with the slightest touch.  

Surprised, Kenshi then held the sword hilt tightly and thought about something, and the demon blade Senjin became extremely soft.  

After that, under his control, the demon blade Senjin continuously changed form as he wanted - transforming, splitting, extending, combining.  

He was amazed. "Did the evil spirit just give me full control of the sword? I did hear its laughter, but why didn't it communicate with me directly?"  

Creeped out a bit, he asked the system if the evil spirit could be any danger to him. The system answered his question this time and told him that the sword was there to help him and it absolutely could not harm him.  

-------------------  

In the training area...  

After just a single day of sword training, Kenshi could already draw and slash his sword as fast as a beginner level Corps member. This astonished Shinobu and Aoi.  

Shinobu was still fine. After all, she had already learned about his sword, so she was just a bit surprised since it was the first time seeing it in action.  

But Aoi was truly dumbstruck. In all her years, this was the first time she had seen such a blade - usable at both long and short range, even able to transform!  

Moreover, the demon blade Senjin's craftsmanship was also very beautiful, making her, who hadn't held a blade for years, feel itchy in her hands.