A theme that is not always as obvious but still present is the idea of family. In the Hunter x Hunter series, family plays a big role in Killua's life. In some fanfics, the reader becomes part of Killua's 'family' in a sense, either by being accepted by his real family or by creating a new family - like bond with him. This can add a lot of depth to the story.
One common theme is adventure. Since the Hunter x Hunter world is full of dangerous and exciting places, fanfics often have the reader and Killua going on quests or exploring new areas. Another theme is friendship. They start to build a strong bond as they face different challenges together.
One common theme is growth. The reader often starts off as a relatively inexperienced character, and through their interactions with Killua, they grow both in terms of their skills as a hunter and in their personal relationships. For example, they might learn how to better control their nen abilities with Killua's help.
The theme of loyalty is quite prevalent too. The OC and Killua form a bond where they are loyal to each other. Also, the idea of power and how to control it or use it for good often comes up. As they face various challenges, they have to figure out how to use their powers effectively and not let it corrupt them, all while their relationship grows and changes.
Well, in these fics, a common theme is the exploration of the Hunter x Hunter universe. Writers often take the reader on a journey to discover different parts of the world, like the Dark Continent. Also, the theme of moral ambiguity is present. The actions of hunters and the world they live in are not always black and white, and the reader character has to navigate through this moral complexity.
The themes usually revolve around family as well. His complex relationship with the Zoldyck family is often explored. Some fanfictions show him trying to reconcile with his family or completely break away. Adventure is another common theme. Since he's a Hunter, fanfictions often send him on exciting adventures, facing new monsters and challenges, which is in line with the spirit of the original 'Hunter x Hunter' series.
Friendship is a very common theme. Gon and Killua have a strong bond, and many fanfictions explore how this friendship grows and endures different trials. For example, they might face a powerful enemy together and their friendship is what helps them get through it.
One popular 'hunter x hunter killua x reader fanfic' is 'A Bond Beyond Hunting'. It beautifully depicts the relationship between Killua and the reader as they go through various adventures in the Hunter x Hunter world. The story focuses on how they grow closer and face challenges together.
Friendship is a very common theme. Their strong bond is often explored further in fanfictions. Another common theme is growth, as they both grow in strength and character throughout the original series, and fanfictions like to expand on that. Adventure is also common as they are hunters.
Another theme is power. In many fanfictions, Killua's sister is portrayed as having unique powers or abilities that she has to learn to control. This could be related to her assassin training or something entirely new. It adds an interesting layer to her character.
One common theme is growth. Biscuit often serves as a mentor to Killua, so a lot of fanfics focus on his growth in strength and character under her guidance.
One common theme is the exploration of Feitan's dark and mysterious nature. Writers often use the reader's perspective to slowly uncover his secrets. Another theme is the idea of an unlikely relationship. Since Feitan is such a complex and somewhat intimidating character, the relationship between him and the reader is often full of tension and growth.