A common theme is the unlikely friendship. Given their different personalities - Kenpachi being bold and battle - hungry and Hanatarou being more timid and healer - like, their friendship development can be an interesting theme.
Well, you can try looking on fanfiction.net. There are often a variety of stories in different genres related to this pairing. Some might focus on their adventures together in the Soul Society, while others could explore a more emotional bond between them.
One common theme is the crossover of their powers. Since Naruto has his ninja abilities and Kenpachi is a powerful Soul Reaper in Bleach, fanfictions often explore how their powers would interact if they were in the same universe.
One common theme is the reader character being in a battle alongside Kenpachi. Since he's a powerful warrior in Bleach, it's exciting to write about fighting together. Another theme is the development of a romantic relationship between the reader and Kenpachi, which can range from a slow - burn love story to an instant attraction. And sometimes, there are themes of the reader helping Kenpachi with his internal struggles, like his love for combat and how it affects his relationships with others.
The theme of friendship across differences is quite common too. Ichigo and Fem Kenpachi come from different backgrounds and have different fighting styles. Fanfictions often explore how they overcome these differences to form a strong bond. This could involve them learning about each other's pasts, cultures, or beliefs. It makes for an interesting exploration of character dynamics and how people can find common ground despite their disparities.
One common theme is power. Kenpachi Zaraki is known for his immense strength, so in crossovers, it often focuses on how his power compares to characters from other series. For example, in crossovers with superhero universes, there's a lot of exploration of who would win in a fight between Kenpachi and a powerful superhero.
One common theme might be the development of the relationship between Kenpachi and Sue. It could start from initial distrust or misunderstanding and gradually grow into a strong bond. Another theme could be the discovery of new powers or abilities within the context of the 'Cave Story' universe as they interact with each other. Also, themes of friendship and loyalty within their relationship might be explored as they face challenges together in the story.
One great toshiro x hanatarou fanfiction might be 'A Bond Beyond Ranks'. It delves into their relationship as they face challenges together in the Soul Society. The way the author portrays their mutual respect and growing friendship is really engaging.
One common theme could be the exploration of Kenpachi Zaraki's character in different situations. Since he is a complex character, fanfics might delve into his backstory or his relationships with other characters in more depth.
Fanfiction.net is also a good place to look. There are many Bleach - related fanfictions on that site. However, the quality may vary, so you might need to sift through some to find the really good toshiro x hanatarou stories.
One idea could be a story where Orihime gets into trouble during a battle and both Kenpachi and Byakuya have to put aside their differences to rescue her. Kenpachi might be all about brute force in the rescue while Byakuya uses his elegant and strategic combat style.