@fsadddfsa—
According to the mtaphysics of this story, reality is multiple time-lines largely formed by divergences (splitting of time-lines), and
these two characters are together in every time-line. Moreover, on some level, minds may become aware of alternate time-lines and even travel across time-lines, sometimes with a time-skip in one direction or the other, but something acts to preserve or restore the appearance within each time-line that it is the one reality. One device or mechanism involves people thinking that events which imply a multiverse are dreamt, rather than experienced.