I'm not sure. It might have some roots in truth, but it could also be a creation of the author's imagination. We don't have enough information to know for certain.
Another theme is friendship. Even when there is a romantic element, their friendship is often a central part of the story. They support each other, have fun together, and rely on each other in difficult times, which is shown in a lot of the fanfictions.
One common theme is growth. They might start out as ordinary characters but through their experiences in the fan fiction, they grow and develop. For instance, they could become more confident or learn important life lessons. Also, the theme of mystery can be present. Maybe they are trying to figure out something about their past or a strange event in their world. This adds an element of intrigue to the story. And of course, the theme of loyalty is often there, showing that they will always be there for each other no matter what.
The story of 'The Girl in the Bunker' is not true. It's a made-up tale that might draw inspiration from various sources but doesn't reflect actual happenings in the real world.