Hisoka's origin story involves his early days as a powerful and somewhat unhinged nen user. Key events include his discovery of his nen abilities and his growing fascination with strong opponents. He has always been on a quest to find and battle those who can give him a good fight, which led him to various parts of the world in search of worthy adversaries.
Hisoka in yandere fanfiction might also display a jealous streak. If he sees the reader interacting with someone else, he could become very agitated and might even start to plan ways to remove that person from the picture. His actions are often unpredictable and a bit on the crazy side, which is typical of a yandere character. For instance, he might give a chilling smile to the person who is talking to the reader, a warning sign of his impending wrath if they don't back off.
Well, Hisoka's origin story in Hunter x Hunter is quite interesting. He hails from Meteor City, a place that's more like a dumping ground for the unwanted. Growing up there, he was exposed to all sorts of things that normal people wouldn't experience. His love for fighting strong opponents probably stems from the fact that in Meteor City, strength was the only way to get what you want. Hisoka's nen abilities are also a product of his environment. He's constantly evolving and seeking new challenges, which is likely a trait he developed while growing up in a place where only the fittest survive.
Hisoka's back story is full of his pursuit of the ultimate battle. He was born with a natural inclination towards combat and a desire to test his limits. As he grew, he became more and more obsessed with finding opponents who could make him feel the thrill of a real fight. His journey has been marked by his encounters with various strong characters in the world he inhabits, and he is always looking for the next big challenge.
In some fanfictions, Gon might initially be shocked. He has seen Hisoka as a somewhat eccentric but strong ally. When he discovers Hisoka's more sinister side, like his love for fighting to the death and his disregard for normal moral boundaries in battle, Gon could be conflicted. He might feel a sense of betrayal because he thought Hisoka was more on the side of 'good' in their adventures. However, Gon's own sense of justice and his unwavering belief in his friends could lead him to confront Hisoka about his true nature.
Hisoka fanfic often focuses on his unpredictable nature. Hisoka is a complex character, so many fanfics explore his motives and desires. For example, some fanfics might dig into why he is so obsessed with strong opponents.
Hisoka is still alive in the manga. The storylines haven't led to his death yet. Maybe there'll be developments in the future, but for now, he's kicking.