Two years later, Li Xing, Kanae, and Mitsuri held their wedding at the Demon Slayer Corps headquarters, with all retired members invited.
After the eradication of Muzan, Tanjiro and his companions returned to Mount Kumo. Zenitsu went back to accompany Jigoro Kuwajima. Though he often wrote letters to Nezuko and Li Xing, neither of them seemed to reply, with only Tanjiro and Kanae writing back to Zenitsu.
The former Hashira had all found their own paths. Tengen Uzui retired with his three wives. Kyojuro Rengoku returned home to inherit his family business. Giyu Tomioka remained as silent as ever and returned to live in Sagiri Mountain. Muichiro Tokito went back to being a lumberjack. Gyomei Himejima became an ascetic monk. The Shinazugawa brothers also retired to their old home. Obanai Iguro, after seemingly taking Li Xing's advice, had set sail to travel the world.
The Butterfly Mansion continued its operations as usual, conducting regular check-ups for the surviving members. With the vast wealth of the Ubuyashiki family, Li Xing was able to relax. His days were spent practicing swordsmanship, accompanied by two beautiful women, making life filled with joy.
...
"Li Yun, if I were to travel to another world, what would I need to do? Would I have to die again? And what about the people around me? Can I take them with me?" Li Xing conversed with Li Yun while lying under a cherry blossom tree, his eyes closed. To an observer, he would simply appear to be sleeping.
"With the current data-based power, direct transmigration is possible. However, your physical condition is not up to par, and the probability of perishing in the void of space is very high. Therefore, I recommend dying again and reincarnating as a soul."
"As for taking others with you, the Infinite Domain should make it possible. But your wives have limited lifespans and cannot accompany you for long. You could ask them if they are willing to become demons."
Li Yun never minced words, directly addressing the crux of the issue. For a member of the Demon Slayer Corps, the thought of becoming a demon would likely be worse than death.
"Sigh, let's leave it at that for now. I'll ask them later. Mitsuri has awakened her mark, and I can only extend her lifespan. If I directly turned her into a demon, I imagine it would be worse than death for her." Li Xing sighed, deciding that for now, he should enjoy life and deal with the future later, living in the present.
...
Time flew by, and in the blink of an eye, eighty years had passed. The former Demon Slayer Corps was long gone, and many of his acquaintances had passed away. Kagaya Ubuyashiki's health had always been poor, and even with Li Xing's help, his lifespan was shorter than average. The current head of the Ubuyashiki family was Kiriya Ubuyashiki.
In the Butterfly Mansion, a white-haired Mitsuri Kanroji lay in Li Xing's arms. To appear normal, Li Xing also took on the guise of an elderly man.
"Mitsuri, human lifespans are always fleeting. I don't want you to leave me. Are you willing to become a demon?" Li Xing softly asked Mitsuri.
"Hoshikun, it's alright. I know your current appearance is a facade. I was a Hashira of the Demon Slayer Corps. If I were to become a demon, I feel as though I would be negating my experiences as a Hashira and betraying those fallen comrades."
"Thank you for taking care of me all these years. The only regret is that Kanae and I did not leave you any offspring. I'm sorry, Hoshikun..." Tears welled up in Mitsuri's eyes as she caressed Li Xing's face. Knowing death was imminent, she still refused his offer.
Li Xing said nothing more, simply holding Mitsuri close and gazing at the cherry blossoms outside the window. As the petals drifted down, Mitsuri's breathing slowed and eventually ceased. She lay peacefully in Li Xing's embrace, a faint smile on her lips.
"Infinite Domain."
Li Xing knew Mitsuri had passed. However, his heart now held a new resolution. He immediately activated the Infinite Domain, placing Mitsuri inside, and simultaneously froze the time within that space.
Turning his gaze elsewhere, he saw Gyutaro and Daki still lying peacefully within a palace. For eighty years, Li Xing had not visited the siblings, leaving them in their dormant state. He felt a pang of guilt for secretly keeping two demons, feeling it was a disservice to the people of the Butterfly Mansion.
"Li Yun, send Gyutaro and Daki to another world. Perhaps we will meet again if fate allows."
After leaving the Infinite Domain, Li Xing went to Shinobu's room, where Kanae was sitting beside her, talking.
"Hoshikun, you're here. How is Mitsuri doing?" Shinobu saw Li Xing enter and already had an inkling of the answer but still asked.
Li Xing smiled, "It's nothing. Let's watch the moon together. We haven't done that in a long time."
He then helped them both to the courtyard, where they looked up at the pure white moon in the sky.
"Hoshikun, the moon is so round, so beautiful," Kanae murmured, leaning against Li Xing's shoulder.
Shinobu looked at the two of them and recalled the past. The first time she saw Li Xing, he was covered in wounds. After he recovered, he shamelessly stayed at the Butterfly Mansion and constantly flirted with Kanae.
Shinobu found Li Xing to be mysterious and, wanting to understand him, asked him to stay. And so, he stayed for a lifetime.
"Yes, the moon is truly beautiful," Shinobu couldn't help but smile. If only her sister were here to see it, it would be even better.
...
And so, the three sat in the courtyard for the entire night. Kanae leaned against Li Xing's shoulder, and eventually, Shinobu also leaned in.
As the first hint of dawn appeared in the sky, Li Xing realized it was morning. The two women beside him, like Mitsuri, had smiles on their faces.
"Is that so? Have you too left me? I'm sorry, please forgive my selfishness for not being able to let you rest in peace. One day, we will meet again."
"Infinite Domain."
Li Xing activated the Infinite Domain once more, placing Kanae and Shinobu inside. Thus, three more people joined the Infinite Domain, each with a smile on their faces. They had not passed away, but were merely asleep.
Li Xing returned to the Butterfly Mansion. He had now reverted to his eighteen-year-old appearance. He entered a room where Aoi Kanzaki and the three younger girls were sleeping. After Muzan's defeat, they had chosen to stay and help Shinobu, never leaving the Butterfly Mansion.
Li Xing cut his hand and then made incisions on the skin of the four girls, infusing them with large amounts of his blood. The four began to slowly regain their youth.
"Human lives are too short. I'm sorry, I can only turn you into demons. I will return," he whispered softly, and then left the Butterfly Mansion. This departure might be for centuries, millennia, or perhaps forever.
After becoming demons, the four girls gradually regained consciousness, faintly hearing Li Xing's last words.
Shortly after leaving the Butterfly Mansion, Li Xing encountered three figures—or rather, demons: Tamayo, Yushiro, and Nezuko, who was unable to turn back into a human.
"Mr. Li Xing, it's been a long time!" Tamayo greeted him first.
Nezuko then ran to Li Xing, "Big Brother Li Xing, I can't turn back into a human? Brother is already gone. Will I continue like this forever? Can you kill me?"
Tears streamed down Nezuko's face as she grabbed Li Xing's hand, begging him to end her life.
Li Xing gently patted Nezuko's head. "Go to the Butterfly Mansion. There are others like you there. Wait for me in this world."
As soon as he finished speaking, Li Xing looked up at the sun, his body began to fade, and soon, he vanished from this world.
"Big Brother Li Xing! Big Brother Li Xing! Where are you? Where did you go? Please don't leave me again, okay? Father is gone, Mother is gone, my younger siblings are gone, Brother is gone, and you're leaving too? Why? Why didn't you take me with you!" Nezuko knelt on the ground, crying out in pain. Immortality was not a blessing; it only brought eternal suffering. Tamayo, seeing this, could only help Nezuko up and head towards the Butterfly Mansion, wondering who the "similar people" Mr. Li Xing mentioned were.
(I'm unsure how to proceed with the writing. I've decided to temporarily remove them to facilitate the narrative. For convenience, I've made Kanae's and Mitsuri's lifespans the same. I feel that introducing characters from other anime or manga breaks the immersion, so I've had the Demon Slayer characters "exit the stage." This is how I will proceed. The next arc should be Naruto. I'll write sporadically. There are no readers anymore; I'm writing for myself. However, if anyone does read this, please leave a rating. I don't mind negative feedback. Thank you.)