First, you need to know both universes well. If it's a crossover with, say, the Naruto and One Piece worlds, understand the rules, characters, and settings of both. For Kakashi, focus on his personality traits like his calmness and intelligence. Then, create a good plot that makes sense for both universes to collide. Maybe a portal opens between the two worlds. Next, keep the characters in - character. Kakashi should act like himself even in a new world. And don't forget to have some action and interesting dialogue to keep the readers engaged.
Kakashi Hatake often visited the local library in the village. There, he noticed a girl who was always engrossed in books about ninjutsu. One day, he approached her to discuss a particular theory. They got into a deep conversation. This led to more meetings, and they became friends. As they spent more time together, Kakashi discovered that she was not only intelligent but also had a great sense of humor. His feelings for her developed into love over time. He expressed his love in a simple yet sincere way by giving her a handmade bookmark with a secret message.
One idea could be a crossover with the Harry Potter universe. Kakashi could be a visiting wizard from another dimension, teaching the students at Hogwarts some of his ninja skills. Another could be a crossover with the Avengers. Kakashi's stealth and combat skills would make him a great addition to the team, and it would be interesting to see how he interacts with the likes of Iron Man and Captain America. A third idea might be a crossover with the Lord of the Rings. Kakashi could be a ranger in Middle - earth, using his Sharingan to detect the presence of orcs and other dark forces.
One possibility could be that Kakashi, with his ninja skills, somehow gets transported to the Percy Jackson universe. He might team up with Percy and use his Sharingan to see through the mist that often confounds mortals in the Percy Jackson world. His combat skills would be a great asset against the various monsters they face.
One great Kakashi Hatake fanfiction is 'A Shinobi's Redemption'. It delves into Kakashi's past traumas and how he overcomes them in a very emotional way. The story has well - written fight scenes and great character development.
Kakashi may become more fatherly. He starts to show more emotions and care, different from his usually aloof self in the original series.
Research the Naruto universe thoroughly. Know the rules, the other characters, and the overall atmosphere. When writing about Kakashi, stay true to his character. He's calm, intelligent, and has his own set of traumas. Incorporate your OC into this world in a believable way. You could also add some plot twists to keep the readers engaged, like the OC having a secret connection to an old enemy of Kakashi.
Well, there's 'Kakashi's Unlikely Love'. In this fanfiction, Kakashi falls for a fellow ninja who is quite different from him. The author does an amazing job of creating chemistry between the two characters through their shared missions and mutual respect. Then there's 'The Love That Heals', which is about a love that helps Kakashi deal with his inner demons. It shows how the power of love can transform a person. And don't forget 'Kakashi's Romantic Adventure' where he embarks on a journey, both physical and emotional, and finds love along the way.
In this fanfiction concept, it could bring a whole new dynamic to the Naruto universe. Kakashi having Naruto as a son would mean a different kind of training for Naruto. Kakashi's calm and strategic mind could shape Naruto in unique ways. Maybe Naruto would inherit Kakashi's love for reading, especially those naughty books, and it could add a comical touch to his character while still maintaining his determination to become Hokage.
One great female Kakashi Hatake fanfiction is 'The Hidden Strength'. It shows a female version of Kakashi in a whole new light, with her facing unique challenges in the ninja world. Her relationships with other characters are also explored in an interesting way.
One great fanfiction could be about Kakashi and Sakura going on a dangerous mission together. In this story, Kakashi's experience and Sakura's medical ninjutsu skills complement each other, and they form a deep bond during the mission.