A cool concept in Naruto x Yu Yu Hakusho fanfiction could be the exploration of different afterlives. In Naruto, there's the idea of the Pure Land, and in Yu Yu Hakusho, there are various spirit realms. Fanfiction could explore what would happen if a character from one series ended up in the afterlife of the other series, and how they would adapt and interact with the entities there.
There's also 'Naruto and Yu Yu Hakusho: A Shared Destiny'. This one is interesting because it delves deep into how the two worlds could co - exist. It's not just about battles but also about the characters learning from each other's cultures and values. It has a lot of character development and the writing style is engaging.
One common theme is power - up. Writers often explore how characters from one series could gain new powers if they were in the other series' world. For instance, Naruto getting some of Yusuke's spirit energy - based powers.
One example could be a fanfic where the Naruto world somehow overlooks the existence of Yu Yu Hakusho elements that have seeped into it. Maybe there's a powerful spirit from Yu Yu Hakusho that's in the Naruto world but is being ignored. Another could be a story where a character who loves Yu Yu Hakusho in the Naruto universe is constantly ridiculed for it, like Naruto himself being into Yu Yu Hakusho but his friends think it's silly.
There's a fanfiction called 'Love in the Demon Realm'. It's a unique take as the reader character finds themselves in a romantic entanglement with a demon from the Yu Yu Hakusho universe. The author does a good job of exploring the cultural and power differences between the human reader and the demon character.
One interesting plot could be that Yusuke from Yu Yu Hakusho gets transported to the world of Inuyasha. He teams up with Inuyasha and his group to fight a common enemy, like a powerful demon that is causing chaos in both their worlds. Yusuke's spirit energy could be a great asset in battles against the demons in Inuyasha's world.
There are fanfictions that focus on character relationships. For example, a story might explore how Kurama from Yu Yu Hakusho and Vegeta from Dragon Ball would interact. They are both proud characters with a lot of power. Or perhaps a story about the younger characters like Gon from Yu Yu Hakusho and Goten from Dragon Ball becoming friends and getting into all sorts of adventures. Some fanfictions also play with the idea of time travel, like a character from Yu Yu Hakusho going back in time to the Dragon Ball era and changing the course of events.
One interesting crossover could be the characters from Yu Yu Hakusho attending Hogwarts. Imagine Yusuke Urameshi in a wizard's robe, trying to figure out how to use a wand. He might get into all sorts of trouble with his hot - headed nature, but his fighting skills could also come in handy during a wizard duel.
One idea could be an OC who is a half - demon from a previously unknown demon clan. They could have unique powers that both intrigue and worry the main characters. For example, the power to manipulate time on a small scale during battles.
The main difference is the gaming element. In 'yu yu hakusho gamer fanfiction', there are often references to game mechanics like leveling up, stats, and skills. Regular Yu Yu Hakusho fanfiction usually focuses more on the original story elements and character relationships without these gaming aspects.
A common theme is power - up. Naruto getting godlike powers similar to those in Yu Yu Hakusho, like enhanced spiritual energy. Another theme could be friendship. Naruto might form new friendships with Yu Yu Hakusho characters while using his new powers.