spoilers:
Endeavor tells Rei that Shoto can't be with the kids anymore and to watch over Toya, while she chastises him for not looking at him and just running away. When Shoto is 5 and stuck in his hard training, a 13 year old Toya unstably vents to Natsuo about their father never paying attention to them with Natsuo brushing him off and Toya reacting even worse. Rei tries to get him to stop, saying he should look at a world beyond his father, but he bites back saying he knows that she was "sold off" by her family and that she's responsible for his creation too.

That winter, his body starts to develop more, leading to his fire changing from red to blue. He tells Endeavor to meet him at Sekoto Peak next day off to see this, but realizing he's been training/still burning himself, and seeing how more deranged Toya's been getting, he enrages at Rei for not stopping it, leading the young Shoto to try and defend her. He goes to Sekoto Peak anyway, and while waiting for one of his parents to show (who both didn't know what else to say to him), he seemingly "dies", as himself and everything around him engulfs in flames, which present Dabi reminiscences about.

In the present, Endeavor says how after losing Toya, there was no turning back and had to pour everything else he had into Shoto at the expense of everything. Rei says how after this, he got worse and worse to the point of her seeing his face in their kids. Fuyumi says how she always wanted to say something about how their family was broken, but was too scared to, and Natsuo says that he is the root of the cause, but also admits if he had attempted to stand up to his father they might have been able to be a family. As Rei mentions they all have their responsibility, and that Endeavor needs to face it too, she brings up how Shoto, who has suffered more than all of them, has started to save them as their hero. Shoto extends his hand to his father, telling him once he's done grieving, they all have to go stop Toya.
end of spoilers

spoilers:
So that appears to be most of the Todoroki family history all come to light. Just like with last chapter, you see how it's pretty much the desperation on everybody's side, without knowing the proper way to express their feelings, that lead to the worst of everything coming to pass. The moral of the story is "LISTEN TO EACH OTHER". I like in the ending where you see each of the family list off why they feel responsible, and even with the kids, it comes off less putting the blame on them and more of their personal guilt that *maybe* things could've changed if they did something more. And how it comes all together to Shoto, the one in the worst situation, turning things around on his own is what can inspire them to come together. Also, "The Wrong Way To Put Out A Fire" is just a really perfect chapter title that summarizes everything.

I am incredibly curious to know where the indication of that final line means. Is this just a "plan for the future" that they'll eventually have to be together to stop Toya, OR are we seriously gonna jump right into a "Find Dabi" arc? After all of Horikoshi's swerves in the story I would not be surprised, though I also wonder what their plan to track him down would even be. Plus the question of if/when we will check back in on comatosed Midoriya too.

Also, one thing I noticed is that there appears to be a slight retcon in the flashback. During the Todoroki family dinner, Fuyumi implied that Toya's "death" was after Rei had already been hospitalized, meanwhile here it's clear that Toya "died" first, which led to Endeavor and Rei's descent into madness.
end of spoilers