1 Prologue

He didn't know whether it was a dream or a vision. But, it was a memory he firmly clung to.

It was during his childhood—at the age of eight, he had traveled to some ruins in the neighboring town to play as he pretended to have adventures.

Under the winter sky of January, when the snow had scarcely started to accumulate, that person appeared in front of his eyes.

——It was a black angel.

The man had black wings growing on his back. The black winged angel appeared to be about his father's age, or perhaps slightly older.

The angel man stooped down so that they were both at eye level and said.

"…..Well then, is it possible you haven't realized it?"

Patting his head, the man put on a smile.

"If so, if it dwells within you, then your world will completely change sooner or later. But, now, now, you shouldn't despair? After all, you—"

Placing a finger on his chest, he said:

"What you carry within you, that cursed flame. Your destiny is extraordinary, whether you like it or not. You, who carry the flame of darkness, are the reincarnation of evil..."

He often could not understand what the man was talking about. He couldn't understand—but the memory remained vivid.

At that moment, he responded to the voice of the friend he'd come exploring with who had been calling out to him, and when faced the man's direction again—it was too late as the black angel was no longer there.

He didn't know whether it was a dream or a vision.

...…

A year later, his world underwent a complete change.

His house, the house where he had lived during his nine years of life, burned in black flames.

The result of the fire was the death of two adults, a woman, and a man. The male, Julian Bertram, 34, and the female, Kaguya Bertram, 32, died in the incident.

Luckily, one person survived the accident, the son of the Bertram couple, Egun Bertram. The firemen found the boy unconscious in the ashes of what was the house.

When the boy regained consciousness, he was asked about the fire. But the boy didn't remember anything about what had happened, he didn't remember his name, he didn't remember his parents, he didn't remember anything.

The boy was diagnosed with global amnesia.

In the absence of any progress in the investigation, the investigators declared it an accident and closed the case. There was no point in investigating something that could not be investigated.

…

8 years later. Tokyo, Japan. Ryujin Residence.

Ryujin Mitsuki is a feminine swordsman recognized worldwide by the title of "storm".

From her childhood, she went to many dojos and defeated them without losing a single time. Her ponytail was like the tail of a black cat, waving in the sky. The blows of her sword style flowed non-stop and were undoubtedly an infinite wind of swords.

Her way of fighting was, in fact, similar to her "storm" title.

However, her sleeping face was like that of an angel.

The curtains were wide open, and the morning sunlight shone in the dark room. But even so, she still slept like a princess and showed no signs of awakening. Her skin was white as light passed through her cheeks. Her long black hair was tied up disorderly, and it was a mess. Her usual stern swordsman's face was also innocent and relaxed.

It had been a while since he had seen her, and she had become pretty. Egun looked at her in fascination.

"No, no, wait. This is not the time to look fascinated at your younger sister." Egun thought.

"Hey, wake up quickly. Breakfast is ready."

Ryujin Egun instilled a loving gesture and shook his shoulders. Just then-

"Nii-sama, an opening!"

The eyes of Mitsuki, who thought that was still sleeping, suddenly opened.

"What?!"

Mitsuki's hands and feet looked like tentacles and suddenly protruded from beneath the blanket.

Mitsuki's soft little hands and legs wrapped around Egun's body. In just a moment, she placed Egun on the bed and hugged him tightly. Toward him, Mitsuki revealed a fearless smile.

"Nii-sama, being drawn by the pretty sleeping face of your younger sister, you became careless. The bed is the battlefield for men and women. This is the Art of Ryujin-Ryuu <Fish needs water to live>".

"You... don't just invent some ridiculous random art."

Mitsuki, who rubbed his face, flirted with Egun, who was stunned and sighed.

"The sensation of Nii-sama, the aroma of Nii-sama, has really been a long time. Although Mitsuki finally had the opportunity to return home yesterday, Nii-sama would not sleep with me. It must be because you are ashamed, so Mitsuki thought of a plan. As expected, you feel ashamed, do you?"

"I'm not ashamed...! Seriously. If it were before, it would be fine. Now we're both high school students, it's disgusting for siblings to be stuck together. I said, don't hug me!"

"Don't treat Mitsuki's pure love between siblings as something unpleasant!"

Ryujin Mitsuki was a female swordsman... However, the fact that she was a severe brocon was really the only drawback.

Though Egun wanted to escape and fought, Mitsuki's hands and legs wrapped firmly around his body did not move. Her hands and legs emitted a faint blue light.

Egun was surprised. It was not the first time he had seen something similar, in fact, he had seen it relatively recently. Since a few months ago, he had seen colors around the people.

The colors were different for each person, as were the intensities of the colors. But there were also people who lacked colors.

Egun didn't know what it meant, and he didn't expect that Mitsuki also had them.

While they were noisy, the blanket slid. Only then did Egun notice a terrifying fact.

"You... What are you wearing? Even though it is already spring, what will we do if you catch a cold?"

Mitsuki wore thin pajamas with which you could almost see the skin beneath.

Her thin waist and round hips showed clearly through the translucent fabric.

"What do you think, Nii-sama? This is Mitsuki updated to high school students. Since Mitsuki had not seen Nii-sama for so long, it is the anniversary where she wants to show her feminine charm to Nii-sama."

Mitsuki, whose face was red, glued her body to Egun's and began rubbing. Her small breasts slowly changed shape.

The bed is a battlefield... Egun began to take deep breaths and calmed down.

"Indeed, you are my pretty little sister... But I will not generate any desire for you. Getaway quickly."

"Kuh. You just said pretty, do you still treat the mature woman, Mitsuki, like a child?"

"What mature woman? Idiot. This is no longer the time for us to sleep, wake up quickly."

"Mitsuki is still sleeping. Fu...Fu..."

"...this is the first time I've seen such a shameless way to sleep."

"Mitsuki is a princess. So if you don't use a proper method to wake up a princess, Mitsuki won't get out of bed."

"No matter what, you were born and raised as a samurai. What is the method of awakening a princess?"

"Speaking of which, the method of awakening a princess is obviously a kiss, Nii-sama. Come."

"No, don't come any closer! Don't come any closer to my face!"

Egun tried to escape again... However, he could not avoid the physical strength of her younger sister.

Impotent, Egun could only drop the bomb.

"You know, Mitsuki, your Nii-chan already has a girlfriend. You should stop playing these games."

The blue light surrounding Mitsuki's body disappeared. At the same time, heat erupted from his body, and Egun made his body awaken. In an instant, he separated from Mitsuki's hands and legs that were imprisoning him and escaped the bed.

"Evil!"

"Who is evil? Why am I evil?"

"You are evil, you are evil because you are deceiving me."

Mitsuki looked at him with puppy eyes.

"...Don't make an expression as if you were a small animal that was abandoned. Seriously, I will force you out of bed."

Egun wrapped his hand around Mitsuki's waist and gently lifted her out of bed. If that is the case, he must quickly finish the job of serving a princess. Mitsuki's expression suddenly glowed.

"Nii-sama! This is the Definitive Secret Art of Ryujin-Ryu <Charge the Princess>!"

"Don't invent a secret art at random! Besides, you know that I am not compatible with Suijin-Ryuu, it is impossible that I can use any art of the familiar style."

"This is exasperating, Nii-sama is really exasperating... "Carrying the princess" is almost like a dream... Even though it was tough to wake up, but Nii-sama did something like a dream in the end... Is this situation what they call a heavenly feeling?"

Egun charged Mitsuki, who had a dreamy expression, and spun.

"Nii-sama, is it true you have a girlfriend?"

"Yes."

"What is she like?"

"She's beautiful, charming, beautiful, nice, beautiful... she's perfect..."

"Nii-sama..."

"Okay, it's over."

"How short! The feeling of floating in the clouds was only a fleeting moment!? It's too short!"

"Hey, before breakfast, change your clothes. That kind of appearance is outrageous."

Egun sighed and brought Mitsuki down, she pursed her lips and launched an attack.

"Since I'm a princess, I can't change myself. Nii-sama, please help me change personally."

"Are you still playing at acting like a princess? Why do you suddenly say such willful words?"

"Nii-sama, didn't you say last night that since we haven't seen each other in so long, you'd do whatever I asked, wouldn't you? We swordsmen must keep our promises!"

"I am not a swordsman..."

"But you're a lancer, you're still a knight. Knights keep their promises!"

Mitsuki was not going to give up. Her Nii-sama had promised her something, and now she had to keep it.

"Even though I said anything is all right, I didn't imagine you'd put in a request like kissing and helping change your clothes. If we did those things as siblings, then it wouldn't be skinship, but perverted acts."

"Anyway, Nii-sama has no lust for Mitsuki, there's no problem then..."

That's the problem, it's not true that I don't feel any lust for my younger sister.

"... Or is it that Nii-sama wants to escape the lure of Mitsuki."

Ugh, she hit the nail on the head.

Mitsuki revealed provocative eyes and raised both hands. Egun was indignant at the gesture.

Because of the challenge launched by her younger sister, responding was her duty as an older brother.

Using his trained mentality, Egun opened his younger sister's pajamas. Just like peeling thin skin, snow-white skin was gradually revealed in front of his eyes. Mitsuki twisted her body.