Perhaps in the fanfiction, Ariel and Eric get married and have to deal with the cultural differences between the underwater world and the human world. For example, Ariel has to learn the proper etiquette in Eric's kingdom while Eric tries to understand the unique traditions of Ariel's mermaid family.
Perhaps in a fanfiction, Ariel and Eric will have a family of their own. They will raise their children to understand both the land and the sea, creating a unique bond between the two worlds.
One possible fanfiction could be that Ariel and Eric discover a hidden underwater kingdom that was lost long ago. They embark on a journey to learn about its history and find that it holds the key to a magical power that can save both the underwater and land worlds from a new threat.
Often, in fanfiction, Ursula can still be a main antagonist. She might come back with a new plan to break up Ariel and Eric, maybe using a different form of magic or disguise this time.
In the fanfiction, a romantic plot could involve Ariel getting the ability to walk on land permanently. Eric then takes her on a tour of his kingdom, showing her all the beautiful places. At sunset, he takes her to a cliff overlooking the ocean and proposes to her, making it a very romantic scene.
One interesting storyline could be Ariel and Eric exploring new lands together that are beyond the sea and the shore they know. They could discover hidden islands with magical creatures and have adventures while learning more about each other's worlds.
One possibility is that they immediately start planning their future. Since they come from two different worlds, they'd have to figure out how to make their relationship work. Maybe they start building a place where both of them can be comfortable, half on land and half in the sea. And they could start spreading the message of love and unity between humans and mer - people.
After the kiss, their relationship could develop in many ways. They might start sharing their dreams with each other. Ariel could tell Eric about her long - held dreams of exploring the human world further, and Eric could share his aspirations of being a great leader. This mutual sharing would bring them closer. Also, they would likely face some opposition, especially from those who don't believe in the union of a human and a mermaid. But this would only make them fight harder for their relationship.
The original story of The Little Mermaid by Hans Christian Andersen is quite different from the Disney version. In the real story, the mermaid makes a deal with the sea witch to gain legs in order to be with the prince. However, every step she takes on land is like walking on knives. In the end, instead of getting a happy ending with the prince, she turns into sea foam because the prince marries someone else.