Kir usually means some big power imbalance baked right into the relationship, so a lot of the tension starts there. Are we talking CEO-employee, professor-student, that sort of thing? The classic conflict is ethics versus desire—characters wrestling with whether what they're doing is right or just succumbing to raw attraction. It's not just 'will they or won't they,' it's 'should they or shouldn't they,' and that moral grey area is where a lot of the emotional heft comes from.
Beyond that, there's always the external pressure. Gossip, professional ruin, social stigma. In a historical setting, it might be absolute scandal; in a modern office romance, it's HR and career consequences. The real juicy stuff for me, though, is the internal power struggle. The character who's supposed to be in charge often feels completely out of control emotionally, and the one in the subordinate position discovers a different kind of power they hold. That flip is way more interesting than any simple forbidden love plot.
My favorite exploration of this is in books like 'The Secret Diary of Miss Miranda Cheever' where the class and age gap creates a constant push-pull. The conflict isn't resolved by just getting together; it's about navigating the new, unbalanced world they've chosen.