A great storyline could revolve around the two brothers having to team up against a common enemy that threatens both their worlds. Sephiroth's immense power from the Final Fantasy universe combined with Naruto's ninja skills could make for some epic battles. Along the way, they could learn more about each other and their respective heritages, with Sephiroth perhaps coming to terms with the more light - hearted and hopeful aspects of Naruto's world.
One possible storyline could be about Sephiroth trying to adapt to the more positive and community - based world of Naruto. He might struggle with the idea of friendship and loyalty that Naruto values so much, while Naruto tries to understand Sephiroth's more complex and often dark motives.
The fanfic could also explore a more emotional storyline. Maybe Sephiroth discovers that he has a brother in Naruto and it changes his whole perspective on life. He could start to question his own dark path and be influenced by Naruto's determination to protect his friends and village. This could lead to a journey of self - discovery for Sephiroth, with Naruto as his guide, and they could face many internal and external challenges together.
It could be a comical take in the fanfic as well. Maybe a crazy inventor or a bumbling wizard accidentally casts a spell that merges the two worlds in a strange way, making Sephiroth Naruto's brother. This would lead to hilarious situations like Sephiroth trying to understand Naruto's love for ramen or Naruto being baffled by Sephiroth's long, flowing hair and his rather dark and brooding personality.
Sephiroth might possess the power to manipulate the elements in a different way compared to Naruto characters. For example, instead of using hand signs for fire jutsu, he could summon dark - tinged flames just by his will. His power over the Lifestream could be reimagined as a connection to a different kind of energy source in the Naruto universe.
The fanfic could also have a more adventurous storyline. Naruto and his love interest go on a dangerous mission together. During this mission, they face many challenges that bring them closer. They rely on each other for survival and in the process, their feelings for each other deepen. This type of storyline combines action and romance, making it exciting for readers.
They could have adventures where they combine their skills. Naruto could use his ninja techniques like shadow clones, and Erza could use her different armors and magic. For example, they might fight against a powerful enemy that is a threat to both their worlds. Naruto's clones could distract the enemy while Erza changes into her strongest armor to deliver a powerful blow.
They could go on adventures to stop ancient evils that are awakening in both their worlds. For instance, an ancient demon from Naruto's world might be summoned by a villain in the DC universe. Together, they would have to use their combined skills to stop it. Naruto could use his Rasengan while Wonder Woman uses her bracelets to deflect attacks.
The fanfic could have a plot about redemption. Suppose Ino's brother has made some mistakes in the past. Naruto, with his forgiving nature, helps him to face his past and make amends. This could involve them going on a journey to right the wrongs that Ino's brother has committed, and during this journey, they grow as ninjas and as friends.
A possible storyline could be that Jinx gets transported to the Naruto universe. She might initially think it's a new place to cause chaos. She starts by attacking a small village, but Naruto shows up to defend it. Instead of fighting her right away, Naruto tries to understand why she's so intent on destruction. Jinx, being confused by Naruto's kindness, starts to question her own motives for causing chaos.
If Naruto is Esdeath's brother in fanfiction, they could embark on adventures across different dimensions. Since Naruto has experience with his own world and Esdeath with hers, they could explore new lands together. They might encounter strange creatures and powerful enemies. Along the way, they could learn from each other's fighting styles and abilities, Naruto teaching Esdeath about chakra and she teaching him about her own brand of combat techniques. And they could also be on a quest to reunite their fragmented family or uncover a long - hidden family secret that has the power to change their worlds.
One possible storyline could be that Naruto learns unique skills from Mikoto. Maybe she teaches him some of the Uchiha clan's secret techniques, like fire - based jutsu, which would be really interesting as Naruto is mainly associated with wind - style. This could also lead to Naruto having a closer connection to the Uchiha, which would change his relationships within the village.
One possible character trait is self - sacrifice. He would be willing to put himself in danger for Naruto's sake. He could also be patient. Naruto can be a bit impulsive, so an older brother would need to be patient with him. He might be a bit of an outcast too, like Naruto was in the village. But instead of being shunned for having the Nine - Tails, he could be shunned for some other reason, like having a different ideology about how the ninja world should be run. This would add depth to his character and his relationship with Naruto.