Let's think about the good side: Maybe the author wants to show us Tanjiro being a grandpa with a lot of grandchildren by his side at his last moments. Then we get to see him reunite with the other pillars when he passed away. Not bad of an ending, right?
Love how the author just keep giving the characters new idea, design and settings. What's next? Cyberpunk or royalty? Do hope to see a traditional japanese theme.
Keep up the good work!!