Kimetsu no Yaiba, also known as Demon Slayer, is an ongoing anime and completed manga that ran for only 4 years. Yet the End of Kimetsu no Yaiba is pretty open for discussion.
The story goes as follows, Tanjiro Kamado’s sister Nezuko is turned into a demon by Muzan Kibutsuji, and so begins his journey to turn her back into a human and defeat the man responsible for her transformation.
The journey takes around 200 chapters until he dies. All the Hashira and Demonslayer Corporation members worked together and won. At the cost of numerous lives, the demon king is dead after 10,000 years.
After that, we fast forward to 100 years later where we see the descendants of the survivors and the reincarnations of the dead living ordinary life in modern-day Japan. School kids going to school, adults heading to work.
But we aren’t given too many clues as to what happened immediately after the fight with Muzan. At least we aren’t told too much. A lot is up to assumption.
What we do know is that Tanjiro, Nezuko, Inosuke, and Zenitsu went back to the old Kamado household and cleaned the place up. They prayed to the dead Kamados before preparing the house for new inhabitants – themselves.
We see small snippets of them enjoying their new peaceful and blissful life with Kanao and the rest of the butterfly girls. We even see Giyu and Sanemi eating together.
We know for a fact that the demon slayers go on to get married and have children of their own. We know that Tanjiro and Kanao get married, Zenitsu and Nezuko get married, and Inosuke and Aoi get married. We also know Giyu and Sanemi get married, but the identities of their wives remain unknown.
They go on to have children, but how many… also cannot be answered. The grandchildren of their grandchildren live peacefully in modern times.
Yet it should also be noted, Tanjiro, Sanemi, and Giyu all unlocked their demon-slayer marks. This means on the day of their 25th birthday, they will die. Sanemi and Giyu will have only 4 years after the final battle to live.
Between these 4 years, they would’ve had at least one small child who they would never be able to help raise.
Tanjiro, already having met his future wife, would be given around a little less than a decade to care for his children. To father them, and to care for them, until he too succumbs.
Although Tanjiro’s situation may differ. Since he is a sun-breathing user he may be able to live longer than age 25. Saying that’s what happened to Yoriichi.Yoriichi lived until his 80s, despite having unlocked his demon slayer mark. Hopefully, he had been able to live long enough to meet his grandkids, and maybe even his great-grandkids.
Inosuke and Zenitsu are guaranteed long lives with their children as they’ve never gotten the demon-slayer mark.
Giyu and Sanemi’s children will inevitably be raised by their wives, after they die, hopefully peacefully.
Tengen, the former sound hashira, would also go on to have children, as we can also see his descendant in the final chapter. Tengen is believed to have lived a long life, as he never unlocked the demon slayer mark. He was never even in the final battle.
As for the other minor characters, characters like Goto, Kotetsu, and so on, they too had children who would have more descendants.
One surviving character who held a different fate would be Kiriya Ubuyashiki, who would go on to become to become the world’s oldest living man. A nice irony considering no one from his family had ever led long lives.
While most of the characters would end up dead at the end of the manga, some survived. And I am happy to say, even though some of those characters didn’t have long post-demon lives, they had beautiful and peaceful post-demon lives.