There might be no time jumper at all.
Simply put, it could be that Takemichi's messing around or ignoring things like in the very first timeline, is what screws thing up and creates unavoidable situations that are bound to happen.
Logically, most of the timelines had Kisaki fucking shit up because that's what he always wanted to do, and had clear plans in mind - plans that always inevitably revolved around Mikey and isolating him from the rest of his friends one way or another.
Takemichi was somewhat important to Kisaki but more tangentially, like an afterthought to get rid of after the important matters were dealt with.
I'd rather have something like that, than a BUT IT WAS ME, DIO! moment. Or an Aizen-style reveal, not sure how it'd work here especially since that card was kinda played by having some of the guys defecting to Izana's group to shock the reader and create some manner of "emotional" suspense.
Anyway, halleluja. The manga seems to be back to the good stuff more consistently, hopefully there won't be soulless, boring padding anymore.