Tanjiro again being a perfect saint, reconciling two siblings even on their last breaths.
If I remember the end of the first series, he has some super-cancer genetic illness, like the inverse of Muzan's mutation.
It's been established that Nezuko can burn her own blood, extended to demon blood, and now demon blood arts. So it sorta follows, but has a limitation. If his super-cancer is demon blood related, then maybe she can.
The comedy relief is what makes this a good series. It's not so far up its own ass with gravitas that it can humiliate its own heroes moments after they win.
It never is intended to excuse their crimes. We're not meant to hate the majority of the demons aside from Muzan and a few of the Upper rankers. Tanjiro always forgives them because they're meant to be pitied for what they've become. This arc should have reinforced that from both side of Nezuko's character, which is and has been the parallel this whole time.Rest of the episode was alright, although I don't see the meaning in flashbacks like these. Yes, villains most of the time have a tragic past that lead them to be the way they are ... but what about it? It doesn't excusive their crimes in the present and it doesn't offer any special insight. Wasted time mostly. If there was anything that could be done to help them, like Tanjiro entering their soul and pulling them back to the human side, that would be something. But alas ...
Nezuko almost went feral with bloodlust. She almost hate human flesh when she did. This arc is a warning to what Nezuko might become if Tanjiro and the others don't always keep an eye on her. She's good yes, she has incredible, unforseen powers for a demon, yes. But she's still very much tempted to become one of Muzan's flock.
Gyutaro realized that Daki/Ume was only fucked up and brutal because he made her that way, and he tried to even take all the blame, and (apparently) whatever afterlife there is, was willing to let her before she reciprocated that loyalty that he always had for her.