Well, one way could be related to Orochimaru's experiments. Orochimaru is always into playing with genetic material and powers. He might have found a way to implant the Rinnegan - related genes into Kakashi, accidentally or on purpose. Another possibility is that in a different timeline or dimension, Kakashi is chosen by some divine force to receive the Rinnegan to fight against an ultimate evil that threatens all the ninja villages.
If Naruto got the Rinnegan in fanfiction, it could completely change the power dynamics. For one, his combat abilities would skyrocket. He could use all the Rinnegan - related jutsus like the Six Paths techniques. This would likely make him even more of a force to be reckoned with against foes like Sasuke or any new threats. It might also change his relationships. For example, his standing among the shinobi villages could become even more dominant, as the Rinnegan is seen as a very powerful and rare dojutsu.
One possible plot could be that Gaara discovers an ancient and powerful jutsu that somehow bestows the Rinnegan upon him. This new power could put him at odds with the other ninja villages as they fear his new - found strength. He might then have to prove that he will use the Rinnegan for good and not for domination.
One possible plot could be that after years of fighting side by side and growing closer, Kakashi finally realizes his deep feelings for Sakura. They start dating secretly at first, not wanting to disrupt the village's harmony. Then, as their relationship blossoms, they decide to get married. Their wedding could be a grand event in the village, with all their friends and comrades coming to celebrate. It could also show how they face challenges together as a married couple, like dealing with new threats to the village while also maintaining their relationship.
The fanfic could start with Naruto being exposed to a strange chakra during a battle with an unknown foe. This chakra mutates his own and results in him getting the Rinnegan. As a result, he gains the ability to understand and communicate with all forms of life, which is one of the Rinnegan's powers. Naruto decides to use this new power to broker peace between different ninja clans and villages. He uses the Animal Path to summon various powerful beasts to act as ambassadors of peace. However, there are still some rogue elements in the ninja world who see Naruto's new power as a threat and try to eliminate him, leading to an all - out battle where Naruto must use his combined powers, including his new Rinnegan abilities, to defend himself and his ideals.
I'm not entirely sure specifically as it could vary greatly depending on the writer's imagination. But generally, in fanfiction, 'kakashi' is a character and 'getting tentacled' might imply some sort of strange or otherworldly encounter involving tentacle - like entities. It could be a very creative and out - of - the - box story idea within the realm of fan - created content.
In a fanfiction, Kakashi and Minato could be on a mission together in a dangerous, unknown territory. There could be traps everywhere. Minato, being the faster one, might rush ahead to scout but accidentally trigger a trap that causes some damage to him. Then, when Kakashi tries to help, he might also get injured by the after - effects of the trap or other hidden threats in the area.
One possible plot twist could be that Naruto, upon getting Sasuke's Rinnegan, starts to see visions of the past and future of the Uchiha clan. This new power might make him question his own beliefs and the relationship between the Senju and Uchiha. He could see the events that led to Sasuke's decision to give him the Rinnegan and struggle with the responsibility that comes with this powerful dojutsu.
One possible plot twist could be that Sakura discovers Kakashi has a secret past she never knew about. Maybe he was involved in some kind of dangerous mission long ago that has consequences in the present. This could put a strain on their relationship as she tries to come to terms with this new information.
One possible plot twist could be that they face opposition from the Hidden Leaf Village. Since same - sex relationships might not be as openly accepted in the traditional ninja world. Another twist could be that they have to go on a dangerous mission together right after getting married, which tests their new relationship. And perhaps there's a secret enemy who wants to break them apart because their union represents a new kind of hope in the village.
One possible plot twist could be that Hanare is actually a spy from an enemy village but has truly fallen in love with Kakashi. She has to choose between her loyalty to her village and her love for him. Another could be that just before the wedding, Kakashi discovers a long - lost family secret that makes him question whether he should get married. For example, he might find out that his family has some sort of curse that could affect Hanare.