If such fanfics exist, a common theme could be the emotional journey of Hanji during pregnancy. It might explore how she copes with the physical and mental changes, and how her relationships with other characters are affected.
Since I don't know the details of the 'hanji great big story', it's hard to say who is involved. But it's likely that Hanji is the central figure, and there might be other characters like friends, family, or foes depending on the nature of the story.
I'm not sure specifically what the 'hanji great big story' is about without more context. It could be a personal story, a fictional tale, or something related to a particular culture or community.
One common theme is friendship. Their relationship, whether it's portrayed as a deep platonic bond or something with a hint of more, is often central. They support each other through tough times, like in battles or when dealing with the politics within their group.
In lemon fanfiction, Levi is often depicted as being very in - control on the surface but secretly having a soft spot for Hanji. His stoic nature gives way to passion in these stories. Hanji, on the other hand, is usually portrayed as being more open - minded and eager to explore the relationship. They both bring out different aspects of each other's personalities.