Definitely. Throughout the manga, it's clear that Yona's love for Hak grows and becomes an important aspect of the story. Their relationship develops in various ways that show her affection for him.
One common theme is adventure. Since the original story has a lot of adventure elements, fanfics often continue this. Yona and Hak go on quests together, facing enemies and exploring new lands, which strengthens their bond.
Yes, there are many. You can start by looking on popular fanfiction websites like Archive of Our Own. There are often stories that focus on the relationship between Hak and Yona and might include a kiss scene. Just search for 'hak and yona' in the search bar and then browse through the results to find ones that seem interesting.
Maybe in the fanfiction, Yona gets pregnant unexpectedly. At first, they are both shocked but then filled with joy. Hak starts building a small house for them to live in. They go through the normal pregnancy experiences like Yona having cravings and Hak trying his best to fulfill them. Their friends also rally around them, offering support and advice for the upcoming new life.
A common characteristic is the strong emphasis on their loyalty to each other. In these fanfics, Hak is always by Yona's side, protecting her no matter what. Yona also shows her trust in Hak.
Another theme is growth. Yona's growth as a person and a leader is often intertwined with her relationship with Hak. As she becomes stronger, their love also evolves. In some fanfictions, it's shown how this growth brings them closer and makes their bond even deeper.
One popular 'Yona of the Dawn Yona x Hak fanfic' is 'The Journey Ahead' which beautifully explores their relationship as they face various challenges together. It has great character development and a lot of sweet moments between Yona and Hak.