~# Keep the chapters coming — Support with Power Stones!
<><><><><><><><>
The Next Morning
Kaidō woke feeling incredibly refreshed, his body lighter, stronger—fundamentally changed. He started to sit up, then paused. Something was weighing him down.
'What the—?' He lifted the blanket. Retsuki was curled up on his chest like a cat, sleeping peacefully.
'Uh... I did not do anything inappropriate, right? Please tell me I did not. Because if I did, that is three years minimum, maximum death penalty...'
"Mm? Oniichan, you are awake?" Retsuki stirred, yawning adorably as she stretched, accentuating her figure.
"Retsuki, why—wait, why are you in my room? And I did not... do anything last night, right?"
"I am sorry, oniichan!" She looked down, embarrassed. "I was scared sleeping alone, so I came here. I am sorry!"
"Silly girl, I am not mad." He ruffled her hair gently. "You do not need to apologize."
"Really?"
"Really! Now come on, let's get up. I will make breakfast!"
"Thank you, oniichan!"
————————————————
After Breakfast
Kaidō purchased a light, flowing dress from the System Lifestyle Shop for Retsuki. Then he took her to the Butterfly Mansion. Girls got along better with other girls.
They arrived at the entrance. Kanae spotted them immediately.
"Oh my! Kaidō-kun, who is this?" She noticed the small girl clutching his hand, peeking out shyly.
"This is my little sister, Retsuki. I will explain later."
"Your sister? She is absolutely adorable! Just as cute as you!" Kanae beamed.
"Uh... anyway, Kanae-nee, I need to ask a favor."
"What is it?"
"I would like Retsuki to work here at the Butterfly Mansion."
"No problem at all! Though, Kaidō-kun, how do you plan to thank me?" She gave him a playful smile.
"Anything within my power."
"Then it is settled! Come on, I will introduce you both at the training grounds."
————————————————
Butterfly Mansion—Training Grounds
Kaidō held Retsuki's hand. "Do not be nervous. Everyone here is kind. Plus, we are close by—if you ever need me, I am just a short flight away."
"Okay, oniichan. I will do my best!"
At the training grounds, the medical staff and Tanjiro's group were present.
"Sister! Oh, Kaidō-kun?" Shinobu noticed them approaching with the girl. "Who is this?"
"Shinobu, this is Kaidō-kun's little sister! She will be joining us here!"
"WAAAHHH! SO CUTE!!" Zenitsu's eyes locked onto Retsuki. "Kaidō-san! Is this your sister?? Did you bring her to introduce her to me??" He stared intensely.
"Oniichan, he is scary! Sob..." Tears welled in Retsuki's eyes.
"Do not cry. I will protect you." Kaidō pulled her behind him. His greatsword floated into position, hovering threateningly. Protective-brother mode: activated.
"Zenitsu, you made my sister cry." Kaidō's smile didn't reach his eyes. "Let me give you some advice: do not even think about pursuing my little sister. Otherwise... I do not mind taking over your training personally. And trust me—I will take very good care of all three of you." His grin widened, revealing small fangs, looking predatory.
"AHHH! Tanjiro, he really IS a demon! Look—his sword is floating! That is definitely a Blood Demon Art!" Zenitsu dove behind Tanjiro.
"Zenitsu, quiet! That is Kaidō-san's family technique," Tanjiro sighed, then bowed apologetically. "I am sorry, Kaidō-san. Please forgive him."
"White-hair! I challenge you!" Inosuke pointed dramatically.
"Once I beat you, I will be—" The rest died in his throat. Kaidō's greatsword hovered at his neck, the edge kissing his skin.
'When did it—I did not even sense it move!' Cold sweat dripped down Inosuke's face.
"Alright, alright, everyone settle down!" Kanae clapped her hands, breaking the tension. "From today forward, Retsuki is part of the Butterfly Mansion family! She will be working and spending time with all of us!" She turned to Retsuki warmly. "If you ever need anything, feel free to come to me."
"Do not worry, Retsuki," Kaidō stroked her hair. "Kanae-nee and the others are wonderful people. I have to go on missions sometimes, so you would be bored home alone. This way you can make friends."
"Okay! I will listen to you, oniichan."
"Then I will leave her in your care, Kanae-nee. Retsuki, I will pick you up tonight."
"Do not worry, Kaidō-kun!"
"I will wait for you, oniichan!"
————————————————
Time Skip
Over the following weeks, Retsuki gradually came out of her shell, transforming into a cheerful, lively young girl thanks to the others at the Butterfly Mansion.
During the day, she helped care for patients; at night, she returned to Kaidō's estate. When he came home from missions, they would chat.
Sometimes he played the flute for her or taught her origami.
Simple, precious moments.
————————————————
One Month Later—Ubuyashiki Estate
Time had flown. The Mugen Train arc was about to begin. Kaidō stood before Kagaya.
"Child, what troubles you?"
"Master, I request permission to accompany the Flame Hashira to investigate the Mugen Train incident."
"Permission granted."
"You are not going to ask why?" Kaidō blinked.
"Because we trust you. Everything you have done for the Corps has been extraordinary," Kagaya smiled gently but firmly.
"Thank you for your faith in me, Master."
"Kyojuro departed three days ago. Tanjiro and his companions left yesterday. Your Kasugai Crow will guide you."
"Understood."
————————————————
On the Road
Leaving the estate, Kaidō encountered Genya Shinazugawa.
"Dragon Hashira-sama!"
"Yo, Genya! How is Water Breathing training coming along?"
"I am getting more proficient every day. I am confident I will master it completely soon."
"Excellent work. Find me once you have perfected it." Kaidō reached into his inventory. "Also, take this."
He handed over the Explosive Gun—a reward he'd never used.
Genya stared in awe. Jet black body with crimson light flowing across it, dragon engravings decorating the barrel. Beautiful and deadly. He loved it instantly; it radiated far more power than his old firearm.
"This is the Explosive Gun. Highly effective against demons. You will discover its abilities through use. I am giving it to you—it will serve you better than me."
"Thank you, Dragon Hashira-sama! I will use it to destroy demons!" Genya's determination burned bright.
————————————————
Mugen Train Station—Three Days Later
"Finally... made it... I am exhausted."
The journey took three days instead of one due to a demon attack. The demon possessed a concealing Blood Demon Art. Without Hyper-Awareness, finding it would have been a nightmare. Once located, he dragged it into the woods, beat it senseless, then decapitated it before continuing.
WHOOOOO!
The Mugen Train's whistle blew; it was about to depart.
"Wait! I am not on yet!" He sprinted and leaped aboard just as it began moving.
————————————————
Inside the Train
Moving through carriages, Kaidō searched for Kyojuro, then heard the unmistakable, booming voice ahead.
"UMAI! UMAI! (Delicious)"
"Perfect timing!" Kaidō grinned. 'I get to witness Rengoku's legendary bento scene!' He headed toward the sound.
"Yo! Rengoku!"
"Hm?" Kyojuro looked up, eyes lighting up. "Young Kaidō! You have arrived! Come, sit! This beef hotpot bento is delicious!"
"Do not mind if I do—I have been traveling for days and am starving!" Kaidō dropped into the seat across and grabbed a bento.
"Kaidō-san! You are here too!" Tanjiro's face brightened.
"Yeah. How have you been, Tanjiro? Is Nezuko doing well?"
"Yes, Kaidō-san! Everything is great! Nezuko is doing wonderfully!" Tanjiro's gratitude was obvious. "Thank you for protecting her back then."
"Do not mention it. Your family took me in. That makes Nezuko my little sister too. What kind of big brother would I be if I did not protect her?"
<><><><><><><><>
~# 18 Advanced Chapters Available on my Patreon!
https://p-atreon.com/dragonnx
(Just remove the hyphen to access Patreon normally.)
~# Every 200 Power Stones = Bonus Chapter!
~# Add to Library!