Well, a really cool concept for naruto tekken crossover fanfiction could be the incorporation of Naruto's transformation powers into Tekken's gameplay. Imagine Naruto transforming into his Nine - Tails form during a fight in Tekken. It would add a whole new level of power and strategy. Also, the story could revolve around the search for a way to return the Naruto characters back to their own world after they've been mysteriously transported to the Tekken world.
One idea could be a crossover where Naruto characters enter the Tekken tournament world. For example, Naruto could use his Rasengan in the Tekken arena against the likes of Kazuya. Another idea is a story where the powers in Tekken are combined with Naruto's ninja techniques. Maybe Jin Kazama could learn some shadow clone jutsu from Naruto and use it in his battles.
Maybe the Akatsuki members could be a villainous wrestling gang. They could use their unique abilities, like Sasori's puppet techniques as part of their wrestling moves. Picture Sasori controlling puppets to attack his opponents in the wrestling ring while the referee is trying to figure out if it's legal or not.
One idea could be a crossover with the 'Dragon Ball' universe. Baby Naruto could meet Goku as a child and they could have a friendly sparring match. Another could be a crossover with 'One Piece', where Naruto ends up on the Going Merry and has adventures with the Straw Hat crew.
One idea could be a character from the Hanyou world ending up in the Naruto universe and having to adapt to chakra. Maybe they could teach the ninja some unique fighting styles from their world in return. Another idea is a crossover of the two worlds' magic systems, like how Inuyasha's Tessaiga might interact with Naruto's Rasengan.
One interesting idea could be a battle scenario where Naruto's ninja skills are pitted against Android 18's superhuman strength. Maybe they start off as opponents but then have to team up to face a greater threat, like an ancient evil that has emerged in both their worlds. Another idea could be a story where Android 18 ends up in the Naruto universe and has to adapt to the ninja way of life. She could learn chakra control and use it in combination with her android powers.
One idea could be that Naruto characters are somehow transported to the Marineford world. For example, Naruto with his powerful jutsu might get involved in the battles at Marineford. He could use his Rasengan against the powerful foes there. Another idea is that the Devil Fruits in the Marineford world have an interesting interaction with the chakra system in Naruto. Maybe a character from Naruto eats a Devil Fruit and gains new and unexpected powers.
One idea could be that Naruto and Link swap worlds. Naruto finds himself in Hyrule and has to figure out how to use the Master Sword while Link ends up in the Ninja world and tries to learn chakra control and ninjutsu. Another idea is a combined quest where characters from both universes team up to defeat a common enemy, like a powerful dark sorcerer who is causing chaos in both the Elemental Nations and Hyrule.
One interesting idea could be the combination of Naruto's world with another popular anime world. For example, if it's crossed with One Piece, Naruto might use his sealing jutsu on Devil Fruits to prevent their misuse. It could also involve Naruto being sealed in a different realm from another anime and having to find a way back while facing new challenges.
One idea could be a scenario where Ichigo and Naruto meet in a strange dimension. They initially misunderstand each other but then realize they have a common goal of protecting their respective worlds. They could team up to fight a new threat that somehow has the power to destroy both the Soul Society and the Hidden Leaf Village.
Perhaps a crossover with 'Grey's Anatomy' in a really wacky and out - of - the - box way. Naruto is suddenly in a modern - day hospital setting. He might use his chakra to heal patients in ways the doctors there have never seen before, creating a lot of confusion and also some amazing medical breakthroughs.