Often, the theme of longing and desire is prevalent. Since their relationship has so many obstacles in the original story, fanfictions tend to play with the idea of their unfulfilled desires. This can be seen in how the lemon elements are incorporated to heighten the sense of yearning between them. Additionally, themes of jealousy and possessiveness might also come up, as both characters have strong personalities and emotions when it comes to each other.
The ending of the anime, Nana, was:
In the end, Nana and Zero got along very well. They experienced many adventures together and supported each other through many difficulties. Zero stayed by Nana's side to protect her and give her strength. In the end, they finally overcame all kinds of difficulties and came together.
Nainai, on the other hand, was a more complicated character. She had experienced many setbacks and pain in the story. In the end, she finally realized her mistake and decided to give up everything in the past and start anew. She also got along well with Zero and experienced many adventures together, becoming the best support and support for each other.
In general, the ending of the animated film was very happy. Everyone got the result they wanted.
You can try searching on fanfiction platforms like Archive of Our Own (AO3). It has a large collection of fanfictions, and you can use the search bar to specifically look for works related to Nana Osaki and Ren Honjo. Another option could be FanFiction.net, although the content quality may vary more there.
Well, for one thing, the Nana manga faced publication issues that led to long hiatuses. Also, the storylines became quite intense and emotional, keeping readers on the edge of their seats.
In the manga of Nana, the ending is complex. It involves various relationship dynamics and life choices that don't have clear-cut resolutions. It leaves you thinking about the characters' futures.