You get a mermaid who's orphaned after evil mermaid kills family because of prophetic dream. Raised by human family whom one his able to breath underwater. As adults they confront evil mermaid wins but mermaid dies from injuries. Mermaid receive internal life for what see have done. Would this fall under fantasy or fiction?
Fiction is an umbrella term that covers all "stories" that aren't "true". So this story would be both Fantasy (the genre) and Fiction (the larger category).
I suspect the OP meant fantasy or Science fiction - if so I'd say fantasy unless there is a strong science vibe around the human characters.
