Well, in some fanfictions, it could be through a dangerous situation. Maybe Lucy is in peril and Natsu's intense fear of losing her makes him realize his love. For example, if she's captured by a powerful enemy, Natsu's desperation to save her and the way his heart races at the thought of her being hurt could be the trigger.
The theme of sacrifice also appears. Natsu might be willing to sacrifice his own well - being or goals for Lucy once he realizes his love. For instance, he could give up a dangerous but lucrative mission to stay and protect her. It's all about showing the depth of his new - found love.
Their relationship might become more affectionate. They could start holding hands, hugging more often, and generally showing more physical closeness.
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.
Well, Natsu is a passionate character. He could react with a lot of excitement. He might pick Lucy up and spin her around, laughing and saying how amazing this is. Or, he could also get a bit worried and start asking Lucy all sorts of questions about her health and what they need to do next.
The theme of unrequited love can also be common in some 'lucy loves natsu fanfiction'. Maybe at the start, Natsu doesn't realize Lucy's feelings or is too focused on other things like his next adventure or his training. This creates a lot of tension and drama in the story, as Lucy tries to hide or express her feelings while Natsu is oblivious.
In the fanfiction, it might be due to a series of events that show Harry's vulnerability and determination. Snape could overhear Harry talking about his fears and his hopes for the wizarding world. This new side of Harry makes Snape re - evaluate his previous views. Harry may be expressing his concerns about protecting everyone, not just for his own glory, which contradicts Snape's prior assumptions.
One possible plotline is that Natsu starts writing in the diary about his confusion regarding his feelings for Lucy. He might write about how he gets jealous when other guys show interest in her. Another plot could be that Lucy accidentally discovers the diary and confronts Natsu about it, which then leads to them finally admitting their feelings for each other.
The chemistry between Natsu and Lucy is full of potential for interesting stories. In fanfiction, authors can take that chemistry and develop it in different ways, like exploring what if Natsu realizes his love in a different situation. Also, their personalities are so distinct yet complementary, which makes for great storytelling in fanfiction.
He might be initially shocked. Natsu is a character full of energy and sometimes a bit clueless. So he could be stunned into silence for a moment before breaking into a huge grin, excited about starting a family with Lucy.
Natsu would likely be extremely guilty. He might immediately stop whatever he was doing and rush to Lucy's side.