In a fanfiction scenario where Goku gets his tail back, it might be due to a genetic experiment gone right. Some scientist in the Dragon Ball world, either good or bad, might be working on Saiyan genetics. They accidentally (or on purpose) trigger the regrowth of Goku's tail. Once he has his tail back, it could change his relationship with other characters. His son Gohan might be really interested in his dad having a tail again. Also, Goku could use his tail in combat in new and unexpected ways, like using it to grapple opponents from a distance or as a distraction during a fight.
It could also be a symbol of a new power - up. In the Dragon Ball series, new physical changes often lead to increased power. So, getting his tail back might mean that Goku is about to reach a new level of strength. Maybe he'll be able to transform into a new form that is related to his Saiyan heritage and the presence of the tail. This could give him an edge in future battles against stronger opponents.
One possible plotline could be that they accidentally meet at a mutual friend's event. The shared memories and the lingering feelings start to resurface. They might start with small talk, gradually realizing how much they still care for each other.
One possible plotline could be that after some time apart, they accidentally meet at a magical event. The old feelings start to resurface as they talk about their shared memories at Hogwarts. They realize that the things that drove them apart were minor compared to their deep connection. So they slowly start to rekindle their relationship.
Another possibility is that a new form of training or power - up in the fanfiction is related to the tail. So Goku is made to keep it for his growth and development as a fighter.
Another plotline could involve an enemy trying to stop Aang from getting his tattoos. They fear that once he has them, he'll become too powerful. So, they send various obstacles in his path, like attacking the place where he's getting the tattoos or trying to corrupt the tattoo artist.
Perhaps in the fanfiction, Tobirama's sickness makes him weak and he starts to reflect on his life and the choices he has made. He could have conversations with his loved ones where he reveals his regrets or hopes. This introspective side of him due to the sickness could add depth to his character. Also, his sickness might be a catalyst for changes in the village he has helped build, as others step up in his absence.
Another plot could involve Naruto being revived due to the strong will of the people. In the Naruto universe, the will of the people can have a strong influence. So, all the people who Naruto has helped and inspired over the years unconsciously create a kind of spiritual energy. This energy is noticed by a sage or some other powerful being who uses it to bring Naruto back. Once revived, Naruto uses his new - found spiritual connection with the people to fight an even greater evil.
One possible plotline could be that Loki meets a girl in a different realm. Maybe she's a powerful sorceress who initially challenges him. As they cross paths more often, they start to see each other's true selves. Loki, who is used to being alone and distrusted, slowly opens up to her. Their relationship could be filled with banter and magical adventures as they face threats to their realms together.
One possible plotline could be that Naruto is granted wings as a result of some ancient and powerful jutsu he accidentally activates. With the wings, he could gain new abilities like enhanced speed in the air and new combat techniques. For example, he might be able to use the wind generated by his flying to create more powerful Rasengan attacks. Another plotline could be that the wings are a gift from a mysterious being who sees Naruto's pure heart and wants to help him in his fight against evil. He then has to learn to control the wings and use them to his advantage in battles against stronger opponents.
A plot could involve Sarada getting hurt in a trap set by a villain. The villain might be targeting the new generation of ninja in the village. As she gets injured, it sets off a chain of events where her friends start to investigate the incident. Sarada, while hurt, could provide some crucial clues from what she saw before getting injured. This would not only be about her physical injury but also about her mental strength as she tries to contribute to the solution while in pain.