Asuka could also be a childhood friend of either Natsu or Lucy. She has known them for a long time and has watched their relationship grow. So, she decides to take matters into her own hands and tells Natsu to kiss Lucy, hoping that it will finally make them realize their true feelings for each other.
Well, one possible plot development could be that Natsu is initially hesitant. After all, he and Lucy have a complex relationship that's more of a deep friendship with some unspoken feelings. But Asuka's words make him start to see Lucy in a new light. He might start to notice little things about her that he hadn't paid much attention to before, like the way her eyes sparkle when she's excited or how she always has a kind word for everyone. This could lead to a series of awkward but sweet moments between them as Natsu tries to figure out his feelings.
One common theme is the exploration of their unspoken feelings. Often, in the series, their relationship is somewhat ambiguous, and fanfiction allows for that to be explored more deeply with the kiss as a climax of those pent - up emotions.
Yes, there are quite a few. You can check out fanfiction websites like FanFiction.net or Archive of Our Own. Just search for 'Lucy and Natsu kiss' and you'll find a variety of stories written by different authors with different takes on their relationship.
Yes. The kiss between Natsu and Lucy is a pivotal moment that adds depth to their relationship in the manga. It comes as a surprise to many but is a welcome development for their love story.