Sanemi here doesn't die from the hunter's mark. You can also see this as an ending where no one died :3

Years after the fight against Muzan, peace was restored to finally happiness, thus ending lives and families destroyed in the clutches of the onia and Muzan Nowadays, despite the many deaths of several humans, hunters... Everything was fine. Now, the majority already had their own families, Kanao and Tanjiro... Uzui has his wife and his son.... Genya, well, Genya was living normally... he still didn't have a family but if Sanemi isn't mistaken, he got a girlfriend...

And him? You might ask yourself... "how?", but he has a small child, a 4-year-old child. The child's mother? died during childbirth, it hurt but Sanemi takes good care of you, even too much. One day he was a tough, aggressive man, but today he feels much better, if I really

Night. Sanemi was in his own room lying on a futon, almost asleep... until he heard some movement in the house. He was alert, you were sleeping... he got up and started walking around the house, until he went to your room and saw you standing awake, with a lit candle for light... He raised an eyebrow almost inaudibly and said

"What happened that you woke up? It's late, child."

Said your father, looking at you as if he wanted to guess what happened