One common theme is the struggle for identity. Since the OC is original, they often have to find their place in the Tokyo Ghoul world dominated by Eto and other known characters. Another theme is friendship or alliance with Eto. Many fanfictions explore how the OC can form a bond with her, either for mutual benefit or out of a sense of shared purpose.
One possible scenario in a Naruto - Kaneki fanfiction could be that Kaneki somehow ends up in the Naruto world. Maybe through a strange portal or some sort of jutsu gone wrong. He might initially struggle to adapt to the different environment and the presence of chakra. But his own unique kagune abilities could be seen as a strange new form of power in the Naruto universe.
One great Eto Yoshimura OC fanfiction is 'The Hidden Path of Eto's Ally'. It delves into the world where an original character becomes intertwined with Eto's journey. The OC in this story has unique powers that add an interesting dynamic to the Tokyo Ghoul universe.
One great 'Kaneki x Reader Fanfiction' is 'A Meeting in the Dark'. It beautifully captures the complex relationship between Kaneki and the reader. The story has a great build - up of emotions and the descriptions of Kaneki's character are very accurate to the original source. Another interesting one is 'Our Unspoken Bond'. It delves deep into the unspoken connection that can exist between the two characters, with some really touching moments.
In some fanfictions, their love is often portrayed as a complex and somewhat tragic relationship. Given their nature as a ghoul and a half - ghoul in the Tokyo Ghoul story, there are often elements of danger and secrecy.
Well, an SSS rated Kaneki fanfiction might also be one that offers a fresh perspective on the Tokyo Ghoul universe. It could introduce new concepts or relationships related to Kaneki that are both believable and exciting. For example, if it creates a new type of bond between Kaneki and another character, whether it's a friendship or a rivalry, and explores that in a way that adds depth to the overall story. Also, the fanfiction should be well - edited with no major grammar or spelling mistakes, because those can really detract from the reading experience and prevent it from getting a high rating.
In a kaneki x tsukiyama lemon fanfiction, the story could be set in the dark and mysterious world they inhabit. Their relationship might be a bit of a forbidden love, given their different natures. The 'lemon' aspect would probably involve some intense emotional and physical interactions. It could show how they support each other through difficult times and how their love, with all its passion, evolves over the course of the story.
Another idea is that Kaneki is brought to the Naruto world by Orochimaru. Orochimaru, being interested in Kaneki's unique physiology, wants to study him. Kaneki has to escape from Orochimaru's clutches and teams up with Naruto and his friends. Along the way, they discover that there are some dark secrets in the Naruto world that are related to Kaneki's past in a strange, unexpected way.
I would recommend 'A New Beginning for Kaneki and Hide' which can be found on Archive of Our Own. It has a unique take on their relationship, exploring what could happen if Hide had a more active role in Kaneki's transformation journey. It's full of emotional moments and great dialogue.
A common theme could be the exploration of unique relationships. Since it involves an original character (oc) and an existing character (eto), the story often focuses on how they interact and develop feelings for each other.