The idea of Eren Yeager in a harem scenario is interesting because it takes a character from a serious and often dark story and puts him in a more light - hearted, relationship - focused situation. It allows for different character interactions that we don't see in the original work.
There are various 'Eren Yeager x Harem' fanfictions. Some stories could be about Eren being in a harem situation where he has to balance his duties and his relationships. Maybe in one, he is training to fight Titans while also navigating his feelings for multiple girls. These fanfictions often play with the existing character dynamics and create new scenarios for the characters to interact in.
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.
Often, in these fanfictions, Eren develops more empathy. He starts to really understand Mikasa's feelings. For example, he might realize how much his actions impact her and become more cautious. He becomes more of a protector instead of just a fighter.
Mikasa is often paired with Dark Eren. Given their long - standing relationship in the original series, it's natural for fanfiction to explore how she reacts to his darker side. She might try to bring him back to the light or be conflicted about her feelings for him.
Armin is often a popular character. He might be like a wise uncle figure to Eren and Mikasa's family, offering advice and support. Another could be Levi. He could be the strict but caring mentor to their children, teaching them important skills.