In a culture where they believe in reincarnation, expect fictional romance with Age gap and such. Since the other party is a semi immortal this is normal. I'm still in chapter 1 and haven't read the novel version if one exist to compare if she really look at him as a child or a brat. But I think first impression will be an adult to a child relationship rather than both adults as equals.
So lets see ....
I want her to succeed running. Anyway both fl and ml are not yet fully develop to live without another so this will be fine. If they are separated there will character development. I have the urge to read if there is a novel but I already have an impression this manga is for the light hearted hence the romcom aspects.
so is this an insubordination magical contract or something to contain her leak?