Let me preface by saying I have zero interest in yaoi or yuri or genderbend. I don't want the story to purely revolve around romance but I am curious where you have seen an action oriented story that introduces a female lead that builds up a compelling relationship with the mc that isn't out of the blue. I really want to avoid cliches of drug induced rape and all these other deus ex means of getting the mc with the fmc. I would also like to see a story where the fmc gets a decent amount of time spent covering her character growth and development. Obviously I want it to be well written as well but if you can share any stories that do a good job building up a good romantic relationship.
Douluo Dalu Coiling Dragon History's Strongest Senior Brother These three come to mind, in that order too, but not in terms of best to worst but in terms of how prominent the romance is in the story. The romance is strong in the first one, very well interweaved into the whole story. Second one has an entire arc or two dedicated to setting up and forming the relationship, a really good arc at that too. The third one is the most like a side story, it slowly progresses alongside the main story but not having much affect on the outcome of the main story.