Kisaki is a smart guy and he treat Takemitchy as his rival because of his ability to stop his plans, At first it's just a gut feeling of Kisaki that Takemitchy seem to be time leaping since it's like he knows all of his plans and put a stop to it, he just confirmed his suspicion after Takemitchy ask him if he is also a time leaper.
Oh wait, mb. I just went back to the chapters where takemitchy confronted him. I thought he said "So you're also a time leaper" instead of "So you are a time leaper" lmao oops
Takemitchy thought Kisaki is also a time leaper since it seems that whenever he succeeded to put a stop in his plans, when he travel to future,Kisaki always created a counter act but it's just turn out Kisaki is just a genius manipulative man.
Spoiler warning ig
MMM I've been thinking about this so much since yesterday, but the only thing throwing me off the theory of Mikey being the other time leaper is that Mikey didn't believe Takemitchy when he said he would go back in time to save him as much as he possibly could when Naoto shot him, but I've been thinking. What if Mikey's "Dark Impulse" can time leap but Mikey can't? Or he time leaps when his "dark impulse" is present but he can't remember anything as his 'normal self? I mean, who knows? But at the same time, how did Kisaki know about time leaping? What I was thinking this whole time was that Hanma was the other time leaper, I mean, even his Kanji revolves around time so maybe? But like, in that one future when Takemitchy saw Hina die, Hanma was present? And the present body is always inanimate when a person time leaps? SO THAT COULD ALSO MEAN THAT ALL THOSE TIMES WHEN MIKEY WAS MIA IN THOSE FUTURES, HE WAS TIME LEAPING?? IDFK MY BRAIN HURTS SO MUCH