One great fanfiction with Natsu being possessive over Lucy is 'A Bond Beyond Measure'. In this story, Natsu's possessiveness is shown through his over - protectiveness towards Lucy. He gets jealous when other guys get too close to her. It adds an interesting dynamic to their relationship as it shows his deep feelings for her in a more intense way.
One common theme is love and protection. Natsu's possessiveness often comes from his deep love for Lucy and his desire to protect her from harm. Another theme is jealousy. When other characters show interest in Lucy, Natsu's possessive side flares up.
The possessive aspect can add depth. For instance, it shows Natsu's intense feelings. If he's possessive, it means he values Lucy a great deal. It can create interesting conflict, like when Lucy might feel smothered but also secretly likes his attention.
One interesting possessive Natsu x Lucy fanfiction could be 'Natsu's Claim'. In this, Natsu might show his possessive side by being overly protective of Lucy during a dangerous mission. He doesn't let anyone else get too close to her while they are in a risky situation, showing his deep care for her in a possessive way.
Their relationship could develop through shared experiences. For example, if they went on adventures together as children, they would learn to trust and rely on each other more. This trust could grow into deeper feelings as they get older.
They can develop their relationship by having small, everyday moments. For example, sharing breakfast together as a family, where they talk about their plans for the day. Natsu could show his love for Lucy by being more protective of her and their family in dangerous situations. Also, they could have inside jokes that only their family understands, which would strengthen their bond.
One character that would be interesting to include is Mirajane. She has a motherly and observant nature. She could be the one to nudge Natsu and Lucy in the right direction when it comes to their relationship. For instance, she might arrange for them to go on a mission together that she knows will bring them closer. Laxus could also be in the fanfiction. His powerful presence can create a sense of danger or protection. If there's an outside threat to the guild while Natsu and Lucy are exploring their relationship, Laxus could be at the forefront of defending the guild, which would impact Natsu and Lucy's situation. And don't forget about Cana. She could be the one to create some light - hearted chaos, like daring Natsu and Lucy to do something that ends up bringing them closer, such as a bet that leads to a shared adventure.
As they travel, their bond deepens. They start to rely on each other more. Natsu becomes more protective of Lucy, and Lucy begins to understand Natsu's impulsive nature better.
She might start to blush furiously. Given her character, she is a bit shy when it comes to romantic matters. And then she might start to stammer out a response, not really sure what to say at first. As she composes herself, she could tell Natsu that she has feelings for him too but in a very gentle and sincere way.