Wow, what a great day for anime. First Attack on Titan, now this. Great episode.
I, too, expected that Zenitsu would continuously behead the sister, proceeding with the "joke" of her being upset about it. Guess not.
Only bad thing: the cliffhanger. With how the brother smirked, we knooooow that Tanjiro's beheading attempt won't succeed, come on.
Anyway, exciting.