Another plot could be set during a time when the Scouts are resting and regrouping. Hanji decides to teach Eren more about the history of the Titans and the world outside the walls. As they study together, they start to develop feelings for each other. But there are also those in the military who oppose their relationship because of Eren's special status as a Titan - shifter. This creates a lot of drama and conflict as they have to fight not only for their relationship but also for their place in the military.
One idea could be that Hanji discovers a new side of Eren during a mission outside the walls. Maybe Eren has a unique way of dealing with the Titans that Hanji finds fascinating, and this leads to a deeper bond between them as they study his abilities together.
Perhaps in the fanfiction, Hanji and Eren are on a mission to retrieve some important data from an abandoned research facility. Along the way, they face various challenges, and Eren starts to see Hanji not just as a superior but as a friend. Hanji, in turn, is impressed by Eren's growth and determination, and their relationship evolves into something more than comradeship. This could involve some emotional moments where they open up to each other about their fears and hopes.
The mystery and the 'forbidden' aspect. Eren has the power of the Titans, which makes him both an asset and a potential threat. Hanji is in a position of authority in the military. A relationship between them could be seen as going against the military's rules or expectations. This 'forbidden love' element adds an exciting layer to the pairing in fanfiction, as they would have to navigate the challenges of secrecy and the possible consequences if their relationship were discovered.
One idea could be exploring Dark Eren's internal struggle in more depth. Maybe he has to make really tough choices between his friends and his new, darker goals. Another could be a scenario where Dark Eren tries to recruit others to his side, and how they react to his changed personality.
One idea could be exploring Eren's family life as a baby. Maybe showing how his parents interacted with him in a more detailed way, like his mother singing lullabies. Another could be a story where baby Eren has some sort of premonition about the future in his dreams, which is a very unique take on his character.
One interesting storyline could be them teaming up against a new, extremely powerful type of Titan that neither has faced before. They have to learn to trust each other's instincts and fighting styles completely.
One interesting idea could be exploring Eren's potential even as a baby in the context of the Attack on Titan world. Maybe showing how his early experiences, even as a baby, might shape his future determination against the Titans.
A possible plot could involve Optimus Prime being mistaken for a new type of Titan at first. The characters in Attack on Titan initially fear him but then realize he's an ally. He could then help in fortifying the walls with his super - strong materials. This would create a new dynamic in the story as the people of the Attack on Titan world have to adapt to having this powerful being around and figure out how to work with him.
One idea could be that the characters from Bnha are transported to the Attack on Titan world. They could use their unique quirks to fight the Titans in ways the AoT characters haven't seen before. For example, Deku could use One for All to launch himself at Titans with incredible force.
Perhaps the friendly titan is a protector of a certain area outside the walls that the humans have not explored much. The story could be about the Survey Corps making an alliance with this titan. The titan guards the area from other dangerous titans, and in return, the humans help the titan when it gets injured. This could lead to a whole new understanding of the titan world and how they can co - exist with the friendly ones.
One common theme is mutual understanding. Given their different personalities, they often have to learn to understand each other deeply in these fanfics. For example, Levi's stoicism and Hanji's exuberance. Another theme is trust. They are in a dangerous world where they need to trust each other completely, and this is often explored.
One common theme is the exploration of Hanji's scientific curiosity about Titans. Hanji is always eager to learn more about them in the original series, and fanfictions often expand on this. Another theme is the idea of coexistence or the possibility of communication with Titans. Some fanfictions also focus on Hanji's moral dilemma when it comes to dealing with Titans, whether to study them or destroy them.