OR WHEN THE ML GOES AND COMMIT DISAPPEARANCE ACTS WITH NO EXPLANATION WHATSOEVER MAKING THE FL THINK OF THE WORST. I mean, I'm okay with it if the ml explains what's happening and says how long he might be gone or tries to tell her that he will try to come back, but that ends up being the cliche hope part.
Because authors need that filler. Most authors are afraid to write the actual relationship, so they force the characters to waffle around until the end where they finally get together. Actually showing a healthy, dynamic, relationship, is apparently 'uninteresting' so they opt out by making it as complicated as possible.

THIS IS THE TYPE OF ISEKAI STORIES I WANNA READ, NO INTENSE DRAMA BETWEEN THE ML AND FL AND IT JUSTS STARTS OUT AS STRANGERS, TO "FRIENDS" TO FRIENDS THEN PARTNERS THEN COUPLE THEN HUSBAND AND WIFE.