I'm not sure. It depends on where the story originated and who wrote it. Sometimes stories labeled as such can be based on real events, but with some fictional elements added.
Well, 'Papa Hemingway in Cuba' isn't a true story. It's more of a creative interpretation or imaginative take on certain themes or ideas related to Hemingway's experiences in Cuba.
One common theme is the exploration of their relationship. Since they are both important characters in Neon Genesis Evangelion, many fanfics delve into how they interact, understand each other, and grow closer. Another theme could be their individual growth within the context of their relationship. For example, Shinji might become more confident through his connection with Rei, and Rei might learn more about human emotions.
Love and acceptance are common themes. These stories often revolve around the characters finding and accepting love, both from others and for themselves.
A really interesting Takashi and Rei love fanfiction could be the one where their love is set against a backdrop of a mysterious disease outbreak. In this fanfic, they have to rely on each other not only for survival but also for emotional support. Their love becomes a source of strength in the face of danger and uncertainty. It might explore how their relationship evolves in such a high - stakes situation.
You can try searching on fanfiction websites like Archive of Our Own (AO3) or FanFiction.net. Just type in'rei and takashi kiss' in the search bar, and it should show relevant stories if there are any.