One idea could be Link and Ilia going on a secret adventure to discover a hidden magic within the Twilight Realm. Maybe they find an ancient artifact that has the power to restore a part of the Twilight Realm that was damaged. Another could be a story where Ilia gets kidnapped by an unknown enemy and Link has to go through a series of difficult trials to rescue her. He could face new and dangerous creatures along the way.
A really interesting plot could be that Link and Ilia find a strange portal that leads to a parallel world where everything is different. In this world, their roles are reversed. Ilia has to be the one to save Link from various threats. They have to learn about this new world, make allies, and find a way back to their own world while also trying to keep their relationship strong in the face of all the challenges.
Link could experience a change in his sense of purpose. Instead of just being the hero who saves the day, he could start to see his role as also protecting Ilia and their relationship. He might become more protective and less reckless in his actions. Ilia could develop a stronger sense of self - worth. She could realize that she has more to offer than just being Link's love interest. She could start to train other villagers in self - defense or become involved in the restoration of Hyrule in a more active way.
One great fanfiction idea could be Link and Zelda's relationship developing during their adventures in Twilight Princess. Maybe they start off as comrades, but as they face more challenges together, they gradually realize their feelings for each other. For example, a moment when Link saves Zelda from a dangerous enemy in the Twilight Realm could be a turning point in their relationship.
One idea could be exploring Midna's backstory in more detail. Maybe how she came to be in the Twilight Realm and her relationships there before meeting Link. Another could be a story where Link has to face a new, previously unknown enemy in the Twilight Realm that is even more powerful than Zant. For example, an ancient evil that was sealed away long ago but is now starting to break free.
You can start by looking on fanfiction websites like Archive of Our Own. There are likely to be many stories tagged with 'Link', 'Zelda', and 'Twilight Princess' that focus on their love. Some popular ones might have high ratings and lots of reviews, which can be a good indicator of quality.
One great 'Link and Zelda Twilight Princess Fanfiction' is 'The Lost Heirloom'. It has an interesting plot where Link discovers an ancient heirloom that has a mysterious connection to Zelda. The story does a wonderful job of capturing the essence of the Twilight Princess world, with detailed descriptions of the characters and their relationships.
You can start by looking on fanfiction.net. It has a large collection of fanfictions related to Link and Zelda Twilight Princess. There are different categories and search filters you can use to narrow down your search based on what you're interested in, like specific characters or plot types.
I'm not sure of the exact title, but there are some fanfictions where the kiss between Link and Zelda in Twilight Princess is part of a prophecy. In these stories, the characters are often unaware of the significance of their actions at first. The kiss then becomes a turning point in the story, not just for their relationship, but for the fate of the Twilight Princess world as well.
One idea could be their adventures in ruling Hyrule together. They might face new threats to the kingdom as a married couple and have to use their combined skills and wisdom to overcome them. For example, dealing with a new dark magic that targets the harmony of the royal family. Another could be their daily life at the castle, like hosting grand balls and diplomatic events, and how they support each other during these. Also, they could embark on secret quests just the two of them to explore hidden parts of Hyrule, strengthening their bond in the process.
One idea could be Link crossing over into a modern world. He'd be confused by the technology like cars and cell phones. Another could be Link teaming up with a character from another game, like Mario. They could combine their skills to defeat a common enemy.
One idea could be Dark Link being a misunderstood entity. Instead of being pure evil, he could be a corrupted form of Link who is trying to break free from the dark magic that binds him. Another plot could involve Dark Link teaming up with Link to defeat a greater evil that threatens Hyrule. This would create an interesting dynamic as they learn to work together despite their differences.