Maybe the Capitol's manipulation during the Games has left such deep scars in Peeta's mind. When he has a flashback, it triggers some sort of defensive or aggressive behavior. And Katniss, being close to him, becomes the unintended victim. For example, if the Capitol had conditioned him to see any potential threat in a certain way, and during a flashback, Katniss might be misinterpreted as a threat.
One possible reason could be the trauma Peeta has endured in the Hunger Games. His flashbacks might make him confused and unable to distinguish between reality and the cruel world of the Games. So, he accidentally hurts Katniss.
It could also be related to his post - traumatic stress disorder. Flashbacks are a common symptom of PTSD. In his mind, he might be reliving a dangerous moment in the Games where he had to fight for survival. And Katniss, who is often by his side, might be in the wrong place at the wrong time. His instinct during the flashback could be to lash out, even though he doesn't really mean to harm her in reality.
Katniss might be initially shocked. Given her own tough exterior, she may quickly try to restrain Peeta without overreacting. She could be more concerned about what's causing his flashback rather than her own injury at first.
One possible reason could be that in this fanfiction, Peeta might have had a past experience with Katniss that made him lose his love for her. For example, if Katniss made a choice that deeply hurt Peeta, like choosing the Games over their relationship in a crucial moment. Another reason could be that the author wants to explore an alternative storyline where Peeta's feelings change due to external influences such as political pressure in the Capitol forcing him to distance himself from Katniss. Or perhaps, in this fanfiction, Peeta meets someone else who makes him realize that his feelings for Katniss were not as deep as he thought.
Katniss would likely be determined to get Peeta back to his normal self. So, instead of just retaliating, she would focus on finding a cure or a way to reverse the hijacking. She might isolate herself with Peeta in a safe place to try and break through to him, using her own memories and emotions to reach the real Peeta hidden inside the hijacked version.
One challenge could be the lack of resources. Their world is often harsh, and getting enough food, medical supplies for the pregnancy and for the baby later would be difficult.
One possible scenario could be that they are finally alone after a long and arduous journey in the Hunger Games. The beach offers a peaceful and secluded place for them to express their deepening feelings. Maybe they have just overcome a major obstacle together and the kiss is a celebration of their survival and new - found closeness.
Peeta and Katniss' love in the fanfiction is also influenced by their different personalities. Peeta is kind - hearted and more open with his emotions, while Katniss is more guarded. His openness gradually breaks down her walls. They learn to understand and accept each other's flaws. For instance, Katniss comes to appreciate Peeta's loyalty and self - sacrifice as they face the challenges together in the story.
They would become more united as they have a new life to protect. Their focus would shift from just each other to their baby, and they would work together even more closely.
Katniss might become more open and less guarded. With Peeta by her side, she could start to trust more easily. Peeta, on the other hand, might become more assertive in protecting Katniss and their new family. His gentle nature could still be there, but he'd have a newfound determination.
They might have some disagreements, like how to raise the child. Katniss, who has grown up in a tough environment, might have different ideas compared to Peeta. But these differences would also help them understand each other better. They would communicate more and work through their issues together, making their relationship more solid.
A lemon fanfiction about Katniss and Peeta in District 13 could be really interesting. It might explore their relationship further in the unique setting of District 13. Maybe it shows how they deal with the new rules and challenges there while also having some romantic or tense moments. It could also focus on how they interact with the other residents of District 13 and how that affects their bond.