Yeah, the second I saw the "Three weeks later" the manga officially derailed from its original concept/premise. Either the author stopped the "one death every seven days" thing, or a bunch of the cast died off-screen. (Or the curse got "paused" by Mai being pregnant, which... ugh.)
I had high hopes since the author also does Montage, but this has become just as chaotic and messy as most horror manga. There's no real foreshadowing of *anything* at this point. I feel like the author either didn't plan all the details of the curse beyond the creepy concept, or they were told to try to stretch the story out longer than they planned so they had to make some big changes that made it incoherent. With a premise like this you can't stretch it on too long or you'll have to veer into ridiculous territory to keep it going. It's always a finite plot.