There could be. Check out various fanfiction communities. They often have filters or tags that can help you find the more family - appropriate stories about Eren and Historia in this situation. It may take some searching, but they do exist.
One idea could be the two of them preparing for the baby. Historia might be learning about different parenting styles, and Eren could be building a nursery. It could show their growth as individuals and as a couple.
A 'historia visual novel' could be about various things. It might be a story set in a historical context, with characters and plots that unfold in a way typical of visual novels. It could focus on a particular era, like the Renaissance or the Victorian age, and tell a fictional story with elements of that time's culture, society, and events.
There could be some, but it really depends on the market and the fan base. Since visual novels are a diverse genre, those with a historical focus might not always get the same level of mainstream attention. But in the communities dedicated to visual novels and historical fiction, there may be some well - known 'historia visual novel' titles that are highly regarded for their storytelling, art, and historical accuracy.
Yes, there might be. The Naruto and Attack on Titan fandoms are both huge, and fans often like to cross over their favorite characters in fanfiction. So it's quite possible to find Eren - from Attack on Titan - in Naruto fanfiction. However, it may not be as common as fanfictions within each respective universe.