One possible plot could be them building a life together after the chaos of the Survey Corps. They might face challenges like adjusting to civilian life, dealing with Levi's past traumas that still haunt him. Maybe they start a small family and have to protect their new life from any remaining threats from the Titans.
It could develop with a lot of mutual understanding. Levi, being the strong but reserved type, would gradually open up more to Petra. And Petra would be there to support him through his nightmares. Their relationship might also grow as they learn to work together in new ways, like running a small business in their post - Survey Corps life.
Well, in levi and petra fanfiction, a prevalent theme is duty. They have a sense of duty towards their mission and their superiors, and this often clashes with their personal feelings. Another is the theme of regret. Maybe Levi regrets not seeing Petra's feelings sooner, or Petra regrets not being more forward. The theme of courage is also there. They show courage in battle, but also in their personal relationships, like having the courage to admit their feelings. These themes help to make the fanfictions more complex and interesting.
In general, Levi x Petra fanfiction often focuses on the potential romantic aspect of their relationship. Given their interactions in the original series, fans like to imagine what could happen between them romantically. This can involve cute moments like shared glances during a meeting, or more intense scenes where they protect each other from Titans. The fanfictions also tend to add more backstory to their relationship, filling in the gaps left by the original story and making their connection seem more real and developed.
In this fanfiction, it could start with Petra suspecting she's pregnant and confiding in a close friend first. Then she tells Levi. Levi's reaction is a mix of pride and fear. The story could then follow their journey through the pregnancy. They might have to deal with shortages of supplies in their world, but Levi is determined to get everything Petra needs. As the due date approaches, they both grow more excited and nervous, and their love for each other deepens even more.
One antagonist could be an old enemy of Levi's who resurfaces during Petra's pregnancy. This enemy wants to take revenge on Levi by targeting what he holds dear, which is now Petra and their unborn baby. They might set up traps or create dangerous situations for the couple. Additionally, there could be some traditionalists in their military organization who don't approve of soldiers having a family and try to make their lives miserable during the pregnancy.
The jealousy can make them more aware of their feelings for each other. When Levi gets jealous, he might start to realize how much Petra means to him. And the same for Petra. It forces them to confront their emotions instead of ignoring them.
The appeal often lies in the characters themselves. Levi is a complex and brooding character, and Petra is a strong and dedicated soldier. Their relationship in the original 'Attack on Titan' series has some underlying tension and respect, which fanfiction writers can develop into a romantic connection, especially the kiss moment which can be a very emotional and exciting part.
One great Levi and Petra fanfiction is 'A Soldier's Promise'. It beautifully portrays their relationship within the military setting. Another is 'Petra's Hope', which delves deep into Petra's feelings for Levi. There's also 'Levi and Petra: Unspoken Bonds' that shows their unspoken connection in a very touching way.