In fanfiction, their possessive relationship can be developed through external threats. Let's say there's a new enemy who is specifically targeting Sakura because of her relationship with Gaara. Gaara becomes extremely possessive and protective, not allowing her out of his sight. Sakura, seeing his worry, also becomes possessive of their time together and doesn't want to be separated from him even for a moment. As they face this threat together, their possessive feelings grow stronger and their relationship deepens.
The possessive relationship could start with Itachi saving Sakura from a dangerous situation. After that, he feels a sense of ownership over her safety. For example, he starts to follow her around discreetly. Sakura might notice this and be a bit annoyed at first but also a little flattered.
In fanfiction, the possessive relationship can start with Kakashi noticing Sakura's growth and potential. He might become possessive as he sees her as a valuable asset to the team and someone he wants to protect at all costs. For example, he could start giving her special training, but in a way that shows his possessive nature, like not allowing others to interfere with her training time.
One way is through shared missions. If they are assigned to a joint mission, they will be forced to work together. During this time, they can start to appreciate each other's skills and personalities. For instance, Sakura's intelligence and quick thinking can complement Gaara's more stoic and powerful approach.
In fanfiction, their relationship can be developed through shared experiences. For example, they could be trapped in a mysterious dimension together. During their time there, they have to rely on each other to survive, which makes them trust one another more.
In such a fanfic, their relationship could be full of tension. Gaara's possessiveness might cause Sakura to push back, creating a cycle of conflict and resolution. As they face various challenges together, they could start to respect each other more. For example, when they are on a mission and have to rely on each other's skills, this mutual dependence could soften their initial stances towards one another and strengthen their relationship.
It can be shown through Itachi's actions. For example, he might not allow other characters to get too close to Sakura. He could give warning looks or subtly use his power to keep others at bay.
They could be paired up for a diplomatic mission to another ninja village. Along the way, they encounter various cultural differences and political intrigues. As they navigate through these situations together, they grow to respect and care for each other more.
In fanfiction, Gaara could be possessive of Sakura due to their different upbringings. Gaara was alone and isolated for a long time, while Sakura grew up in a more normal ninja community. His possessiveness could stem from his envy of her normalcy and his desire to keep that 'light' in his life.
They could start as rivals in academics or sports. For example, if there's a science competition in the highschool, both Itachi and Sakura are determined to win. However, as they prepare, they start to respect each other's intelligence and hard work. This mutual respect could be the first step in developing a relationship.
They could start as study partners. Itachi helps Sakura with more difficult subjects like math or history. Through these study sessions, they get to know each other's personalities better. Sakura might notice how gentle Itachi is despite his cold exterior. This could lead to them having lunch together regularly, and then eventually going on outings outside of school, like to the park or the library.