In a casino on the Banfield family's capital planet, the manager was anxiously checking his appearance.

He was accompanied by a group of burly security guards, their faces also tense with nervousness.

One of them asked the manager.

"Are you sure about this, sir?"

The manager, fighting the urge to run away, steeled himself and replied.

He wanted to flee just as much as they did.

"Of course. I am the manager of this casino. It is my duty to deal with anyone and everyone with a firm resolve."

The manager and his men were heading towards an area lined with slot machines.

As they approached, the other patrons looked on in surprise, wondering what was happening.

A casino is a place where money is wagered, and they often had to deal with customers agitated by their wins and losses.

Sometimes, rude customers would even resort to violence.

In such cases, the casino's formidable security guards would restrain them.

And the person they were now nervously confronting was—

"Aaaahhh!! It ate my money again!! Give it back! My wife is really going to punish me this time!!"

—It was Yasushi, screaming as he slapped the machine with his open palms.

At first glance, he looked like nothing more than an unimpressive man in a kimono, but this was the man who had been the sword instructor to Liam, the head of the Banfield family.

He was a master of the One-Flash Style, a school that had slaughtered the Empire's Sword Saints.

The manager and security guards of a single planet's casino would be no match for him.

Furthermore, Liam respected Yasushi.

Picking a fight with Yasushi was the same as picking a fight with Liam.

It was no wonder the manager and his men were tense.

Still, the manager put on a smile and addressed Yasushi.

"Sir, if you keep hitting the machine like that, you'll break it."

"Huh?!"

Yasushi, noticing the manager and his men, was startled for a moment, but he quickly straightened his posture and crossed his arms.

His posture was that of a martial artist—or at least, it could be seen that way.

Yasushi gave a theatrical cough.

"Ahem! My apologies. However, don't you think the settings on this machine are a bit strange?"

Having lost heavily, Yasushi seemed unconvinced by the machine's settings.

The manager was troubled.

"I swear on my life we are not doing anything dishonest. This is all a matter of luck."

Normally, this would be the point where they'd take the customer to the back or throw them out of the casino.

But with Yasushi, it was a different story.

After all, Yasushi was a high-roller for the casino.

He was a regular patron and always had a large sum of money on him.

What's more, for some reason, he lost significantly more than the average person, making him a more profitable customer than most.

Even setting all that aside, he was not someone they wanted to deal with.

Ideally, they'd prefer he didn't come, but turning him away could infuriate Liam.

The manager was exercising the utmost caution.

Still, Yasushi persisted.

"But isn't this a bit much? I was hoping you'd show some of your famous generosity, Manager."

As Yasushi looked on, hoping to get even a little of his money back, one of the security guards operated a terminal.

A screen appeared in mid-air, displaying the face of his wife, Nina.

The intelligent-looking woman with long black hair and glasses was smiling, but her eyes were not.

Yasushi's face turned pale.

"Eek!?"

"Yasu-kun, you shouldn't cause trouble for the people at the casino. Besides, I told you that Yasuyuki is home today and that you should play with him, didn't I? I wonder why you're at the casino, hmmm?"

"Well, you see, Yasuyuki is getting bigger now, and—"

"I told you to play with him, didn't I? ...Didn't I?"

"—Yes."

As Yasushi meekly agreed, the call ended.

The manager handed the dejected Yasushi a bag containing a souvenir.

Inside were high-class sweets.

"Master Yasushi, thank you very much for your patronage today."

The manager bowed deeply, and all the security guards bowed in unison.

"Thank you very much!"

Overwhelmed by the pressure from the manager and his men, Yasushi trudged out of the casino.

◇

Back at Yasushi's mansion, Fuuka and Yasuyuki were present.

"I wonder what that Rinhou is up to now."

Fuuka was in the garden swinging a wooden sword, but her movements were like a choreographed dance.

Yasuyuki was captivated by her fluid, continuous motions.

Having been raised as a knight under Klaus, he could tell that her movements were those of a first-class swordswoman.

"Big Sis Fuuka, it looks like you're dancing."

For Fuuka, it was just a way to work up a sweat and kill time, but when she realized Yasuyuki was impressed, she felt the urge to show off.

"Want me to show you an even more amazing technique?"

"Really?!"

Yasuyuki's joy was plain to see, but—Fuuka sensed an unpleasant presence, tossed aside her wooden sword, and grabbed her own katana that she had placed nearby.

She quickly rushed to Yasuyuki's side and took a battle stance.

"Big Sis Fuuka?"

"Someone's here. Yasuyuki, you be careful too."

As Fuuka scanned her surroundings, she heard a faint chuckle.

Looking up at the roof, she saw Rinhou, a katana slung over her shoulder.

She had discarded her scabbard, and Fuuka felt a sense of wrongness.

"Rinhou, what are you—"

Fuuka gasped at the aura emanating from Rinhou, with whom she had grown up as a sister.

The basis of the One-Flash Style was a lightning-fast draw, so the sight of her without a scabbard was nothing but bizarre.

Even more so, the powerful aura Rinhou was emitting overwhelmed Fuuka.

Rinhou leaped down from the roof and landed on the ground.

But her stance, with both feet and her left hand on the ground, her body low, looked like that of a beast.

"Practicing your little dance? How carefree. You're weaker than me, shouldn't you be training harder?"

Though her taunting words were the same as usual, what Rinhou was emitting was killing intent.

Fuuka's eyes widened, and she unleashed a flash.

"Kuh!"

The two flashes collided in mid-air and burst apart.

The clash of the two magic-infused flashes looked like a shower of sparks.

Sparks rained down on the mansion's garden, but among them were mixed flashes of black light.

Fuuka glared at Rinhou.

"That aura—it's the same as that inhuman thing, Pharabal!"

The current Rinhou was emitting the same presence as Pharabal, the self-proclaimed demon lord that Liam had once destroyed.

The One-Flash Style was originally a sword art meant to protect the weak from the inhuman.

To be harboring the same—negative energy—was a contradiction.

Rinhou's mouth stretched into a crescent-moon smile.

"If it makes me stronger, I don't mind falling from humanity—I'm going to become the strongest swordsman."

Rinhou's flashes grew more intense.

Fuuka unleashed her own flashes to counter, but she was gradually being pushed back.

"Have you really fallen that far?!"

Fuuka shouted at Rinhou.

Her anguished cry, not wanting her sister to go down that path, must have reached Rinhou.

But Rinhou's expression vanished.

"—Are you telling me to just watch your backs? You two just keep moving forward, leaving me behind. How could someone like you ever understand how I feel?"

In that instant, Rinhou's flashes grew sharper.

The power of each strike increased, and Fuuka's flashes were overpowered and blown away one after another.

While unleashing flashes, Rinhou kicked off the ground and closed in on Fuuka.

As she drew near, Fuuka drew her swords.

"I'll drag you back!"

Rinhou replied.

"Go ahead and try, if you think you can."

Flashes erupted around the two, destroying the mansion's garden.

As the two drew their blades and clashed, sparks flew violently.

Yasuyuki, watching from behind Fuuka, was too scared to move.

"Both of you, stop! Big Sis Rinhou!!"

Yasuyuki called out, but his voice didn't reach Rinhou.

A downward strike from Rinhou slammed Fuuka, who was blocking with her two swords, to the ground.

"What's wrong? For all your big talk about dragging me back, you can't do a thing. As I thought, you're beneath me."

Looking down at Fuuka, who was on her back on the ground, Rinhou was triumphant.

On Rinhou's cheek—a flash from Fuuka grazed it.

It inflicted a tiny wound, and a little blood seeped out.

Fuuka grinned.

"This is what you get for getting cocky."

Fuuka kicked Rinhou away, quickly got to her feet, and readied her twin swords.

Rinhou touched her own cheek, then looked at her blood-stained palm.

Seeing this, a chill ran down Fuuka's spine.

Rinhou's gaze shifted from her palm to Fuuka.

"—I'll kill you."

She had heard those words many times before, but this time, they were filled with murderous intent.

Fuuka instinctively took a defensive stance, but she was a fraction of a second too late as her body was slashed all over.

She barely managed to protect her vital points, but blood gushed from her arms and legs.

Rinhou, splattered with the blood, was smiling.

Fuuka looked at the transformed Rinhou with a face full of despair.

"You... you bastard—"

Fuuka, collapsed on the ground, tried to get up—but Rinhou stomped on her head.

Rinhou spoke in a low, cold voice as she raised her sword to strike Fuuka down.

"Bye-bye."

With lifeless eyes, she was about to kill Fuuka, who had grown up as her sister—when it happened.

"Stop it already!"

Yasuyuki leaped out, shielding Fuuka with his own body.

Seeing this, a faint light returned to Rinhou's eyes.

"Yasu...yuki?"

"Big Sis Rinhou, you're going too far. There's no reason to do this!"

Denied in such a strong tone, Rinhou shook her head.

She probably couldn't bear being glared at by Yasuyuki.

"No. This is what a swordsman—I... I'm—"

It seemed there was still hesitation in her heart.

Yasuyuki's words had still reached her.

But, sensing a human presence, Rinhou turned around.

"I'm home—huh?! Why is the garden a mess?! This is definitely one of those things my wife is going to yell at me for!!"

Yasushi had returned to the mansion.

Rinhou was visibly flustered.

"M-Master—kuh!?"

Not wanting Yasushi to see her in her current state, Rinhou leaped over the mansion wall and fled.

Yasushi rushed over to Yasuyuki and Fuuka, shocked at their battered state.

"Hey, what happened, Yasuyuki?! And who did this to Fuuka?!"

Fuuka couldn't say anything.

Not about how Rinhou had fallen as a swordsman, nor about her own defeat.

But Yasuyuki was different.

"Stop Big Sis Rinhou. If you don't, something terrible is going to happen."

Yasuyuki pleaded with Yasushi to stop Rinhou.

The request left Yasushi dumbfounded.

"—Huh?"

◇

After defeating Fuuka, Rinhou wandered aimlessly.

As she did, she heard a commotion.

"I sense my senior disciple's presence over there."

Is something happening? Slightly curious, she went to take a look and saw Liam punching Edward, sending him flying.

From Rinhou's perspective, Edward was a failure as a swordsman of the One-Flash Style.

Even Rinhou, who had fallen to darkness, would not unleash a flash at her master.

And yet, there he was, unleashing flashes at Liam and running away.

"Ah, this is grounds for expulsion. I wonder if my senior disciple will dispose of him?"

She watched with a smirk, but then Rinhou noticed something.

Liam wasn't using the One-Flash Style.

In the first place, Edward was no match for Liam.

If he wanted to kill him, it would be over in an instant, yet he was deliberately fighting him with his fists.

For Rinhou, it felt like a betrayal.

"So my ideal senior disciple, a swordsman of the One-Flash Style, is just a mere parent after all. Ah, I feel like I've just been shown a farce."

Then, even Ellen jumped in.

It was probably to protect her precious disciple, but from Rinhou's point of view, it was unbearable to watch.

Furthermore—the fact that Liam was about to end the commotion without punishing Edward was more than she could bear.

"Soft. You're too soft, senior disciple."

Unable to hold back any longer, Rinhou found herself stepping out in front of Liam and the others.

When Rinhou appeared, Liam and his group grew wary.

But Rinhou's gaze was fixed on Liam.

"Bringing parental affection into the One-Flash Style... you've gotten pretty soft, haven't you, senior disciple?"