A plotline might be that Sasuke gets involved in some dangerous mission or political intrigue where he has to pretend to be with another woman to gain information or an advantage. Sakura suspects he's cheating because she doesn't know the full story. And Itachi could be a factor in Sasuke's decision - maybe he's following some path he thinks Itachi would have taken, even if it means hurting Sakura in the process.
One possible plotline could be that Sasuke, feeling conflicted by his past and the secrets he holds, distances himself from Sakura and starts to develop an inappropriate emotional connection with someone else, which Sakura misinterprets as cheating. As for Itachi's role, perhaps his memories or the influence he had on Sasuke play into Sasuke's actions, like Sasuke trying to live up to some ideal Itachi had that made him question his relationship with Sakura.
Maybe Sasuke is haunted by his past actions and the people he has lost, including Itachi. He starts to act out and gets too close to a female acquaintance who understands his pain. Sakura, being in love with Sasuke, quickly notices the change in his behavior and believes he's cheating. The idea of Itachi could be constantly in Sasuke's mind, making him feel like he doesn't deserve Sakura's love and leading him to engage in behavior that looks like cheating from the outside.
In some fanfictions, it could be that Sakura is under a genjutsu (illusion technique). The genjutsu makes her act in ways that seem like she is cheating on Sasuke. She doesn't realize what she is doing until it's almost too late, and Sasuke has to figure out what is really going on to save their relationship.
One possible plotline could be that after Sasuke has finally returned to the village and reconciled with Sakura, they start to rebuild their relationship. They go on dates, share their feelings and experiences during their time apart, and gradually their love deepens until they reach a point of expressing their physical love for each other.
Perhaps Sasuke uses Sakura to get closer to some information. He might know that Sakura has connections or knowledge that can help him in his quest for revenge or for protecting the village. So he uses her in a strategic way while she is initially unaware of his motives. As the story progresses, their relationship could develop in complex ways.
Maybe Sakura teaches Sasuke about emotional control. Sasuke has always been brooding and angry, and Sakura, with her more empathetic nature, could show him how to manage his emotions better. This could lead to Sasuke becoming a more well - rounded ninja and a better teammate.
Maybe Sasuke is jealous because Sakura has achieved some great feat in the ninja world and is getting a lot of attention. In the fanfic, this could lead to Sasuke training even harder to prove himself worthy of her. Sakura, on the other hand, might be confused by Sasuke's sudden distance. She could try to reach out to him, but Sasuke's pride and jealousy keep him from being receptive. It could all come to a head during a dangerous encounter with a powerful enemy where they finally communicate their feelings.
In a fanfic, it could be that Sakura is wrongly accused of cheating on Sasuke. Maybe a false rumor spreads in the village. The fanfic could then focus on how Sakura and Sasuke deal with this rumor. Sasuke might initially be angry but then realizes he should trust Sakura more. And Sakura has to fight against the judgment of the village while trying to prove her loyalty to Sasuke.
One possible plotline could be Sasuke becoming increasingly possessive as Sakura's popularity or friendships grow. He might start to isolate her from others, thinking it's for her own good.
A possible plotline could be that Sakura discovers she has a rare and dangerous pregnancy complication. Sasuke, initially shocked, vows to protect her and find a solution. He might go on a journey to find a rare herb or seek the help of a reclusive healer. Meanwhile, Sakura is in the village, trying to stay strong and use her medical skills to keep herself and the baby alive as long as possible.
A plotline might involve Sakura facing a lot of judgment from the village. But she stands strong and raises the child with the help of her friends like Naruto and Ino. They support her emotionally and sometimes even materially. As for Sasuke, he might be on a journey of self - discovery and when he hears about the pregnancy, he has to decide whether his path still lies away from Konoha and his family or if he should change his ways.
A possible plotline could be that they are both on a mission to rescue their kidnapped comrades. They have to work together, using their unique ninja skills. Female Sasuke with her lightning - fast attacks and Sakura with her super - strong punches.