Adventure is also a theme that pops up often. They might go on an adventure together, like exploring a mysterious place or facing a powerful enemy. This theme allows for a lot of action and development in their relationship. And sometimes, the theme of self - discovery is there. They learn more about themselves as they interact with each other.
One more common theme is family. Since Tsuna has a complex family situation, fanfiction sometimes incorporates how Haru fits into that family dynamic or how their relationship is affected by Tsuna's family. It can be really interesting to see how the two interact within the context of family.
Love is a very common theme. It shows how Tsuna and Haru might fall in love or their existing love story. Another common theme is friendship, as they are friends in the original and fanfiction often explores different aspects of their friendship.
One common theme is friendship turning into love. Since they start as friends in the original work, many fanfictions explore how that relationship deepens into romantic feelings over time.
Overcoming obstacles together is also a frequent theme. They might face external threats or misunderstandings. In some fanfics, there are rival characters who try to come between them, but Tsuna and Haru always find a way to overcome these difficulties and strengthen their bond in the process.
Love and friendship are common themes. Since they are characters from the same series, their relationship can be explored in terms of how a friendship can turn into something more. Also, growth is a theme. For example, Tsuna might grow more confident in his relationship with Haru, and Haru might grow more independent while still being close to Tsuna.
A prevalent theme is the exploration of their relationship in the context of the overall story world. Since they are part of a larger narrative, fanfictions might show how their bond affects the events around them. Additionally, themes of loyalty often come up. They are loyal to each other, and this loyalty can be tested in various fictional scenarios created by the fanfiction authors. It makes for an interesting read as it shows the depth of their connection.
There is a fanfiction where Tsuna and Haru are paired up for a school project. As they work on it, they start to understand each other better and feelings develop. This one focuses a lot on their character development and the little moments between them that are really sweet.
There are fanfictions where Tsuna and Haru start as friends and then gradually develop deeper feelings for each other. These stories often explore their different personalities and how they complement one another. For example, Tsuna's shyness and Haru's outgoing nature can create interesting dynamics in the relationship. They might go on a journey where they discover new things about themselves and each other, and the story unfolds as their relationship blossoms.
Often, there are themes of adventure. Haru might go on adventures with water as a sort of guiding or powerful force. For example, he could be exploring underwater worlds or using water to overcome obstacles in a magical journey. This type of theme can make for very exciting stories.
One common theme is friendship evolving into something more. Writers often explore how Kazu and Haru's relationship deepens over time, from just being friends to having romantic feelings. Another theme could be adventure. They might go on adventures together and through those experiences, their bond gets stronger.
One common theme is growth. They often start as two very different individuals, and through their interactions, they grow both personally and in their relationship. For example, Hibari might be more reserved and Haru more outgoing, and they learn from each other's traits.
Another place to search is FanFiction.net. There are many different categories and fandoms represented there. Just use the search function and type in 'tsuna x haru' to see what comes up. However, the quality of the stories can vary widely, so you may need to sift through some to find the really good ones.