I'm not sure there are many specific fanfics just on this one aspect. However, you could start by looking on fanfic platforms like Archive of Our Own. Search for 'Banana Fish Eiji kidnapped' and you might find some relevant works. Some fanfics may explore different motives for the kidnapping, such as using Eiji to get to Ash or for some political gain within the complex world of Banana Fish.
In a fanfic, Eiji could get injured while exploring an abandoned building that has some connection to the Banana Fish mystery. Maybe he trips and falls, hitting his head. This could lead to a series of events where Ash has to take care of him, and in the process, their bond deepens as they share more personal stories while Eiji recovers.
In 'banana fish fanfic', friendship and loyalty are often explored as themes. Since the relationship between Ash and Eiji is so central in the original, fanfics may expand on that. They might show how their friendship endures through different trials. Another theme can be the exploration of the criminal underworld in more detail. Writers could create new storylines within that seedy world, perhaps introducing new characters who interact with the main cast in interesting ways.
Banana Fish is not based on real events. It's a fictional narrative that takes the reader/viewer into a made-up world with its own unique plot and characters.
Well, first, try searching on AO3. There are tags related to Banana Fish. You can look for fanfics with high kudos or a lot of bookmarks. These usually indicate that other readers have liked them. Also, follow some Banana Fish fanfic writers on platforms like Twitter. They might announce when they release a new, potentially great, fanfic. And don't forget to read the reviews of the fanfics. If a lot of people are praising it, it's likely to be a good one.
The best place to find 'banana fish fanfic' is definitely AO3. It not only has a vast number of fanfics but also a very active community. This means that new and updated fanfics are constantly being added. Additionally, the site allows for detailed tagging and categorization. For example, if you want to read a fanfic that focuses on the relationship between Ash and Eiji, you can easily find it by searching for the relevant tags. Some smaller, more niche fanfic communities might also have 'banana fish fanfic', but they can be harder to find.
Banana Fish is purely fictional. The plot, characters, and events were all imagined by the writer to create an engaging and unique narrative. There's no real-life inspiration behind it.