You, When Did You Become So Gentle?

Demon Slayer Corps headquarters, infirmary.

"Did you say the mark?" Tsugikuni Kokushibo stared at his younger sister in astonishment.

More precisely, he was staring at the red mark on his younger sister's cheek.

It really did look somewhat similar to Yoriichi's.

Yuko gave a slight nod. "At the time, I nearly died at the hands of a demon. It was the mark that suddenly awakened and saved my life."

"From what I understand, it should be an ability that can only be mastered after the body surpasses its limits."

Tsugikuni Kokushibo stared at Yuko in shock, completely unable to understand her words.

Before Yuko, neither the Demon Slayer Corps nor Kokushibo had considered the mark on Yoriichi's forehead anything more than a birthmark.

That was until Yuko awakened her own mark as well.

After a moment of silence, Kokushibo clenched his fist. "You said the body becomes stronger?"

"Mm. I don't know the principle behind it, but I can clearly feel the increase in my strength."

After resting for several days, Yuko had recovered from her weakness. She could clearly feel the changes in her body.

Kokushibo abruptly rose to his feet and gripped the hilt at his waist. "Come with me to the Training Ground."

He wanted to verify this conjecture himself.

How could something so absurd possibly exist?

The physician beside them hurriedly said, "How can you do that? Miss Yuko hasn't fully recovered yet."

"I think I'm already fine... Cough, cough." Yuko smiled as she spoke, but her calm expression shifted slightly, and she couldn't stop herself from coughing twice.

The physician sighed. "Your lungs suffered severe frostbite. With the current level of medical care, it can't be completely cured. I'm afraid your use of the Breathing Technique will be affected as well."

Kokushibo frowned slightly. "What happened?"

Yuko shook her head. "I was merely tricked by that demon."

Those who awakened the mark would not live past the age of twenty-five.

Knowing this, Yuko didn't particularly care about her lung condition.

Besides, compared with those swordsmen who had just learned the Breathing Technique before dying horribly at the hands of demons, she was far better off.

At least she was still alive.

To survive after going onto the battlefield was already incredibly fortunate.

Seeing this, Kokushibo could no longer force her. "Then get some proper rest."

With that, he turned to leave.

"Wait." Yuko rose from the sickbed.

The physician hurriedly tried to support her.

Yuko declined her kindness. "Doctor, you should understand my condition."

The physician paused, then sighed. "I'll find a way to deal with your lung problems."

"Please try not to engage in strenuous exercise."

"Thank you." Yuko smiled faintly, then turned to Kokushibo. "Brother, let's go to the Training Ground."

Kokushibo frowned as he looked at her, standing motionless in place.

Yuko tilted her head. "What is it?"

"..." After a long silence, Kokushibo abruptly asked, "When did you become so gentle?"

For some inexplicable reason, she gave him the feeling that someone nearing death had suddenly become kind in their final words.

"..." Veins slowly surfaced on Yuko's temple. She forced out a deathly smile. "Oh, really? So you're the type who feels uncomfortable if nobody insults you?"

"You should have said so earlier. Yuko could curse you from morning till night."

Even she got goosebumps from the words she had just said, but as long as she could disgust Kokushibo, it counted as a victory.

Kokushibo ignored her this time and left the infirmary.

Tsugikuni Yuko took a deep breath.

Stay calm. Stay calm.

That damned sour-faced jealous man. Today, I'm going to use the full package to bully my elder brother!

The Training Ground Kokushibo referred to was not the Demon Slayer Corps' Training Ground. People often used that place, and Kokushibo didn't like being watched.

The Training Ground he meant was the mountain behind the Demon Slayer Corps.

The three siblings often went there to temper their sword skills.

When they arrived at the Training Ground, Yuko put down her Nichirin Blade and reached for the wooden sword resting to one side.

"Use a real sword."

Kokushibo's voice interrupted her movement. Yuko paused, then slowly drew her Nichirin Blade and stood opposite her elder brother.

Yuko raised her eyes slightly and looked at Kokushibo, who had also drawn his Nichirin Blade.

"Come on."

As soon as the words left their mouths, two voices rang out in unison.

"Moon Breathing: First Form - Dark Moon, Evening Palace."

Their quick-draw slashes, too fast for ordinary people to see, collided at that moment, and the blades let out a crisp, mournful cry.

Kokushibo's pupils contracted slightly, and the arm bracing against Yuko's Nichirin Blade trembled faintly.

He was actually being overpowered in strength...

A man's body was naturally stronger than a woman's.

That was an indisputable fact.

It was also why Kokushibo had never thought highly of her despite Yuko becoming a member of the Demon Slayer Corps.

It wasn't as if he had never sparred with Yuko before. He had always defeated her with ease, and he had never experienced pressure as immense as this.

She was clearly still using the Breathing Technique she was not good at.

It was as if she had been reborn.

"Moon Breathing: Second Form - Bathing in Moon!"

"Water Breathing: Form Four - Striking Tide!"

Back and forth, Yuko blocked every one of Kokushibo's attacks.

Was Yuko, like Yoriichi, going to leave him behind as well?

Kokushibo grew increasingly unwilling to accept it, and the Nichirin Blade in his hand moved with ever greater disorder.

With her physical abilities greatly enhanced, Yuko calmly defended against her elder brother's fierce attacks.

She wasn't stupid. Although she had never read the manga and didn't have a detailed understanding of Tsugikuni Kokushibo, after twenty years together, she had long since seen through his jealous nature.

He was jealous of Yoriichi's talent every moment of every day. Or rather, he could accept the fact that he was inferior to others, but he could never accept being surpassed by his own younger brother and younger sister.

Especially when it was his twin brother.

He was jealous of the talents possessed by his own family.

"Cough..."

The instant Yuko's breathing became disordered because of her lung condition, Kokushibo seized the opportunity.

"Moon Breathing: Sixth Form - Perpetual Night, Solitary Moon - Infinite!"

Several rapid, crescent-shaped slashes shot toward Yuko.

The greatest strength of Moon Breathing lay in the finer crescent slashes attached to each main slash.

They could easily cover a wide area.

"Hiss~"

Yuko calmly adjusted her breathing, exhaling a faint white mist.

"Snow Breathing: First Form - Blizzard!"

A white blizzard mixed with a trace of cold swept away all the incoming crescent slashes.

At the same time, Kokushibo, who had never seen Snow Breathing before, was caught off guard and swept into the air by Yuko's Sword Style.

"Snow Breathing?!" Kokushibo's heart was filled with shock as he lost his balance in midair.

It wasn't just her strength—even her self-created Breathing Technique was... Didn't this mean that Yuko's talent was on par with his own?

If he couldn't even surpass his younger sister, how could he ever surpass that person?

The raging blizzard battered Kokushibo's body without pause. After all, this was not a fight to the death, so Yuko was using the back of her blade.

The frustration of defeat, combined with the jealousy nearly bursting out of him, caused Kokushibo's body temperature to rise constantly, while his pulse rapidly quickened.

"Moon Breathing: Fifth Form - Calamitous Moon Spiral!"

Kokushibo's body spun in midair. As he swung his Nichirin Blade, enormous vortex-shaped blades formed around him and knocked the blizzard away.

The two attacks collided and completely canceled each other out.