I made a prediction about the direction I felt this show was going a few reviews back, then it went and totally defied my expectations by having last episode happen. Demon Slayer, it seems, wanted it both ways though, making Tanjiro the badass and also in need of rescuing. So my predictions ended up coming to fruition in the end anyway.
Episode 20 is more of a wind down to this arc than anything. With the senior slayers showing up to clean up the massacre that was ultimately the corps’ own doing, we get what has become the standard expectation for this show and see an expositive flashback showing us just how tragic the demon’s stories are.
I’m kind of on the fence about this particular quirk of the series. While it is interesting to delve into the reasons behind why a person would go down such a terrible path and end up as such a creature, but it’s difficult for me to feel too much sympathy for them when they are still literal monsters.

This time, we focus on the spider sister character, who was saved and taken in by Rui. The leader of this fake little family himself has no memory of his life as a human, thus he takes in these other demons and forces them to play along in his twisted little game of house. Horribly abusing them if they drop their facade for even a moment. Which shows how devoid of any humanity he actually is.
It’s a pretty horrific situation all things considered, but as we find out during a pretty unnerving interrogation scene, she has still killed dozens of humans in her time as a demon. Literally melting them into a jelly. So it’s difficult to feel too sorry for a literal demon.

They all die anyway; Giyū shows up and effortlessly finishes off Spider King Rui, as I said he would and the sister is finished off by the insect stance slayer Shinobu. Who herself is a pretty unnerving character, using poisons and torture on demons with a bright smile on her face.
The ending to this arc has certainly been as dramatic as it has been masterful in its animation, but it ultimately did exist as that measuring bar I was talking about a few reviews back. We needed to show how far Tanjiro and the gang still had to in order to lead into some kind of training arc/episode leading into the final six episodes of this series.

Tanjiro, Inosuke and Zenitsu are all in a pretty bad place right now, so I’d imagine we’d see them taken back to HQ and maybe get a little more insight into the slayer corps proper. Weird, why am I suddenly getting HunterXHunter flashbacks…