Genres
Romantasy
Fantasy and romance structurally interdependent: remove the romance and the plot falls apart.
Romantasy (fantasy romance) is fantasy whose worldbuilding and romance plot are structurally interdependent; the distinguishing test is that the plot falls apart if you remove the romance. That separates it from "fantasy with a romance subplot".
Like all romance, it inherits the genre-wide baseline expectation of an emotionally satisfying, optimistic ending (HEA/HFN), which romance readers treat as close to a hard rule.