"I'm back," Mizuki said, tilting her head slightly, sounding a bit shy.
Yoriichi stood behind the door and said with a smile, "It's good that you've returned."
"Come inside."
He stepped aside.
"Mhm." Mizuki replied carelessly, lowering her head as she walked into the house.
Yoriichi noticed her distraction and asked, "What's wrong? Did something unpleasant happen outside?"
Compared to his youth, the elderly Yoriichi exuded a certain mundane vitality belonging to mortals.
"Nothing... I'm just a little unused to it since I haven't been home in so long," Mizuki offered a casual excuse.
Yoriichi chuckled, "Is there ever a time you feel unused to things?"
Mizuki pursed her lips and looked up at Yoriichi.
His fiery red long hair now contained many strands of white, and wrinkles had begun to appear around his eyes.
Yoriichi was truly old.
Mizuki felt a blockage in her heart, and unable to converse much with her brother, she sullenly went to sleep.
Early the next morning, when Yoriichi came to Mizuki's room, he found that she was already gone.
This was probably the worst decision Mizuki had ever made.
Perhaps after this departure, she would never see Yoriichi again.
In ancient times, people reaching fifty were considered elderly, and every extra year of life was a surprise.
Yet, she hadn't stayed by Yoriichi's side to take care of him; instead, she had run away... and many years had passed in a blink.
Mizuki wandered aimlessly across the land.
When she returned to her hometown again, she had actually walked there unconsciously.
How many years had it been?
Ten years? Or twenty?
The effect of longevity made it nearly impossible for Mizuki to accurately judge the passage of time.
The passage of years had brought many changes within the town, and Mizuki felt uneasy as she approached the familiar front door.
Her fingers hovered in front of the door; she hesitated to knock.
Yoriichi... was he still alive?
Mizuki began to regret whether she should have run away last time.
Perhaps the owner of the house had changed.
The moment Mizuki drew back her arm, the large door opened from the inside.
She hadn't sensed anyone approaching.
Mizuki was surprised for a moment and subconsciously looked up.
What appeared before her eyes was a frail, elderly man with a full head of white hair.
Ancient wrinkles covered the old man's cheeks, making him look both aged and unsightly.
When she saw the familiar Demon Slayer Mark on the old man's cheek, tears welled up in Mizuki's eyes.
Yoriichi smiled gently, the wrinkles on his face moving; it wasn't a particularly beautiful smile.
"Welcome back."
Mizuki's lips trembled continuously, finally forming a single sound.
"I'm sorry..."
She shouldn't have left... Inside the house, Mizuki bowed her head deeply, afraid to face Yoriichi.
Across from her, Yoriichi said softly, "Mizuki, you didn't do anything wrong."
"But I haven't come back all these years."
Yoriichi said gently, "I understand your pain."
Mizuki subconsciously looked up, her eyes filled with tears.
Realizing her action, she quickly lowered her head again.
Yoriichi suddenly took out several envelopes from his embrace and handed them to her.
"What are these?" Mizuki asked, taking them confusedly.
Yoriichi smiled, "They are letters from Tankichi."
Due to Mizuki's encouragement, Yoriichi and Tankichi had maintained frequent contact ever since.
Mizuki opened the first letter, which contained greetings from Tankichi's family to the siblings.
It also inquired about her condition.
Her sudden departure that day had been noticed by the thoughtful Tankichi.
Tankichi comforted her in the letter.
Most of the remaining envelopes were also greetings, expressing hope that they would visit again.
Judging by the yellowing of the envelopes, it was impossible to tell how many years old they were.
Mizuki was touched, but also felt guilty.
Yoriichi said softly, "Birth, old age, sickness, and death are the norm for mortals. We should all face them calmly, shouldn't we?"
"But I..."
"Mizuki, don't you still have things left undone?"
Mizuki paused slightly. Defeating Muzan?
Mizuki nodded heavily.
Yoriichi smiled and, rarely, made a joke: "Get some rest early. Tomorrow morning, I plan to test your swordsmanship."
"Good night."
"Good night," Mizuki murmured.
Had she returned this time only to send off her brother?
The vitality within Yoriichi was dwindling; he had nearly reached the end of his life.
He probably wouldn't live much longer.
She had truly returned just in time.
Mizuki thought self-mockingly.
After she fell asleep, Yoriichi, in the other room, felt a strange sensation inexplicably rise in his heart.
Was it unease?
Or something else?
This strange feeling compelled him to leave the house and the town late at night.
He went alone to the outskirts.
It was only upon reaching the outskirts that Yoriichi finally understood the strange throbbing in his heart.
It was the unbreakable blood connection of twins.
"This is impossible... Why are you still alive?"
"A swordsman who develops the Demon Slayer Mark is destined not to live past twenty-five."
"Why are you the only one... who has lived until now..."
What Kokushibou could not comprehend was that after sixty years, the younger brother who should have died long ago reappeared before him like a nightmare.
Tears streamed from Yoriichi's eyes: "How pathetic, Brother..."
He was actually being pitied by this creature who was once his own younger brother but was now frail and aged?
Kokushibou's heart, which had grown cold due to Demonization, stirred once more.
But... he didn't feel any anger.
Instead, that address of "Brother" caused a strange wavering within him.
It was an emotion called sorrow.
This was one of the few emotionally charged statements he had ever heard from his emotionally detached younger brother.
But as long as the other party was a Demon Slayer, he had to cut down the intruder, even if it was his younger brother from his human life.
Even in this current, fragile state.
Just as Kokushibou was about to draw his sword, Yoriichi drew the nichirin blade at his waist one step ahead of him.
The atmosphere instantly became tense. Yoriichi's aura pressed down on Kokushibou's shoulders, almost solidified, like a massive boulder.
The stance adopted by this frail, aged creature was utterly flawless.
"I'm here."
As if announcing death, Yoriichi's extreme speed accompanied his aged voice.
It was so fast that Kokushibou barely had time to react.
The next moment.
Second only to the Demon King Muzan, the strongest among the demons, Upper Rank One.
A streak of fresh blood spurted from Kokushibou's neck.
Why... why are you the only one who is always special... Even though you are a Demon Slayer Mark swordsman, even though you are nothing but skin and bones, the power and speed of your strike are virtually identical to your prime.
Memories Kokushibou had long forgotten resurfaced in his mind.
Kokushibou's jealousy, which had been dormant for decades, flared up again.
I hate you, I want to kill you so badly!
Kokushibou turned around furiously, his hideous face resembling a true demon.
But at the same time, Kokushibou knew he wouldn't have a chance to dodge the next move.
Yoriichi's next strike would certainly take his head.
The intense agitation and sense of defeat felt as if they would grind Kokushibou's internal organs into paste.
However... Yoriichi hesitated and never swung the next strike; he simply stood there, and after his lifespan ran out, he departed the world.