What if

HHHMMMMMMMMM
Well, he'd be with Tanjiro and Giyuu when fighting Akaza in the Infinity fortress
If he doesn't die there
He'd have some serious emotional damage with THAT thing that happened Tanjiro after defeating Muzan.

Yeah

I think rengoku would fight upper moon 1 and not akaza

What if Mui and Genya lived after the Kokushibo fight?

Yeah I think they would still die during sunrise countdown mainly due to their injuries

Or they would be sent to the butterfly mansion to be treated

Well, maybe not Genya-
Cause you know-
His demon eating thing-

Yeah I guess

MY F**KING EARS-
MY CLASSMATES-

My life would be better and I wouldn’t cry at night that’s for damn sure

Then rendonut wouldn't be a donut anymore

rengoku won't commit die