I'm just gonna ignore this ending and assume that the ending was chapter 204. I wanted to see Nezuko and Zenitsu, not their grand grand children. It is kinda looks like Harry Potter's ending but more f'ed up way.
I'm really wondering that after fighting with Muzan, this manga will be over or is there a bigger demon than muzan? I mean i don't think Muzan created all these demons. There must be a demon god or sth. :)
BTW this one has much better translation. Thanks.