The concept that everyone is fated to die as a result of Satsuki's actions has been referenced 3 times: twice from Kai and once from Satsuki right at the start of the manga.
But they don't add up. Kai claims this started when Satsuki enrolled. Satsuki pins everything on the day she first saved Komachi, a year later. And I'm more willing to side with her, not only because she's speaking from the future.
We've seen Satsuki trace a clear chain of events after Michiru nearly burned Miho to death: Michiru's love took a twisted turn after she saw Satsuki attack Miho in the pool. Satsuki only got so aggressive with Miho because of the way she treated Komachi. Miho only relapsed into bullying Komachi because... Satsuki saved her that first time.
Continuing forward: Seo took advantage of Michiru's instability to trick her into killing Miho over some unstated history. Miho found out about it and now seems to be inciting a war trying to get Seo killed. Events keep rippling forward and this sense of mob justice is affecting more of the school.
I'm fairly sure there's a misdirection going on.
Satsuki's overwhelming guilt leaves her feeling responsible even for those minor connections. We know she's been obsessively saving people for years yet it's the first time with Komachi which is most important. Which leads me to believe fate isn't truly responsible for the ultimate tragedy; that's a direct result of Satsuki's own actions. There's no evidence of fate literally demanding a death for every life Satsuki saves, despite Kai's superstitions.
But it's undeniable there's an insane amount of deaths happening exclusively around her. There is a supernatural force at work here, just one that might not work like Kai thinks. After all Michiru's death didn't cause it to stop. Both meanings, metaphorical and literal, could simultaneously be true. And the answer probably isn't as simple as "let one person die to save everyone."
The question always comes back to Komachi's role. Why does Satsuki put her at the heart of it? Why not one step removed, blame saving Miho in the pool?
Well Komachi enrolled at the same time as Satsuki. She's happened to be present for many accidental deaths, including the choking boy and the girl in the library. And there's something deeply wrong with her that seems to get ignored because both sides paint her as nothing but an innocent victim.
(Once again it's impossible not to draw connections to Tokiko, which could be a great meta-misdirection on its own but I'm sure Komachi won't end up unsympathetic either.)
I don't think we're near the end yet but I do think we're at the start of Satsuki finally waking up a little to Komachi's danger. And maybe Sensei can start applying some more scientific method to the mechanisms of fate.