On a more serious note, this wouldn't feel a tad bit unrealistic if we were given some more fights with Kanao beforehand (just knowing she's a successor isn't really enough). Hoping future chapters make up for that.
@Mireaderc I believe she was mixing poisons and the last ingredient for the cóctel of death was her own blood, so is not Kanao 1vs1 you could say this is Shinobu's sure kill technique specially made for an upper moon because she knew she couldn't win normally, he says that the girl is adapting to his speed but I'm sure he's getting slower without realizing
Kanao spoke more on this chapter than anything on the whole series.
It was always stablished than she is stonger than Tanjirou (till now) so let's hope a great fight with sissy Douma showing his full power and maybe Kanao with the marks.