Well, it could be about Kotetsu and Izumo facing a really tough mission that turns into a nightmare. Maybe they get trapped in a genjutsu created by a powerful enemy. In this genjutsu, they relive their worst memories, like failing important missions in the past. And they have to find a way to break free together, relying on their friendship and the skills they've developed over time.
It could be a rogue ninja who has a vendetta against Konoha. This ninja might target Kotetsu and Izumo specifically because they are guards of the village gates. They see them as easy targets to start their revenge plan against Konoha.
Another jutsu Naruto could learn is a defensive one. Given that Kotetsu and Izumo have to protect themselves and others, they might teach Naruto a jutsu that creates a stronger shield or barrier. This would enhance Naruto's survivability in battles, especially against powerful opponents. It could be a jutsu that combines chakra control and some form of elemental manipulation, which Naruto can then adapt to his own style with his large chakra reserves.
Well, Naruto might incorporate more teamwork - based tactics into his combat style. Since Kotetsu and Izumo are used to working together, they could instill in Naruto the importance of coordinating with his allies. He could start using moves that complement his teammates' abilities more often, and be more aware of his position in a group fight.
Well, it could be about Naruto being transported to the world where Nightmare Moon exists. Maybe he has to team up with the local ponies to stop Nightmare Moon from causing more chaos. He could use his ninja skills, like his shadow clone jutsu, to outwit her and her minions.
One great 'naruto kotetsu fanfic' is 'Kotetsu's Journey'. It really delves into Kotetsu's character, showing his growth from a relatively unknown shinobi to someone with a more significant role. It has a great plot that weaves in with the main Naruto storyline in an interesting way.
Well, it could be about Naruto characters somehow getting involved with Gundam technology in a nightmarish scenario. Maybe Naruto and his friends find themselves in a world where Gundam mechas are being used for evil, and they have to fight against it using their ninja skills. It could also involve some sort of dark magic or curse related to the Gundam machines that they need to break.
A Caius Ballad nightmare fanfic could have a plot where Caius is plunged into a nightmare that blurs the lines between reality and the dream world. He might encounter distorted versions of people he knows, or be in a situation where he is constantly running from an unseen threat. The nightmare could also be a result of a curse or some dark magic, and as he tries to escape, he discovers secrets about himself or his past that he didn't know before. This could lead to a journey of self - discovery within the nightmare, all while trying to break free from it.
Archive of Our Own (AO3) is also a great place. It has a well - organized tagging system, so you can easily search for 'naruto kotetsu fanfic' and find relevant stories.
It could be that Aria is in a strange and dark dream world, facing her deepest fears. Maybe she's lost in a maze of some sort and being chased by shadowy creatures.
Well, it could be about the Hogwarts kitchen being in chaos. Maybe the house - elves go on strike and the students have to try and cook. It would be a mess with magic spells going wrong in the kitchen, like a spell to make the food cook faster makes it explode instead.