One possible plot could be a crossover battle. Naruto, with his powerful ninja skills like Rasengan and Shadow Clone Jutsu, could face off against Majin Android 21's unique abilities. Maybe they start off as enemies but then realize they have a common foe. For example, an evil entity that threatens both their worlds. Naruto could use his determination and leadership skills, while Majin Android 21 could bring her combat and energy - based powers to the table. In the end, they might combine their forces and develop a new friendship or alliance.
Perhaps a story where Naruto is sent to the world of Dragon Ball by some strange magic. There, he meets Majin Android 21. She is initially intrigued by this strange being from another world. They start to train together. Naruto teaches her some of his ninja discipline, and she shows him advanced combat strategies from her world. Eventually, they work together to stop a powerful villain in the Dragon Ball universe who is threatening to invade other worlds as well.
One interesting plot could be a character who has the Majin Buu bloodline being transported to the Naruto universe. This character might initially struggle to control their unique powers, which are a combination of Majin Buu's abilities like regeneration and the ability to turn things into candy, and the chakra - based powers in Naruto. For example, they could accidentally turn a ninja's weapon into candy during a fight, creating a chaotic and humorous situation. Then, they would have to learn to harness their powers properly to fit into this new world and perhaps use their powers to help the ninja villages against a common enemy.
Well, it could be about Naruto having the unique powers of Majin Buu. Maybe he'd have the ability to regenerate like Buu. And his personality might change a bit, being more unpredictable. He could use Buu's techniques in battles against his enemies in the Naruto world.
Naruto's chakra - based powers and Majin Android 21's energy - based powers could either clash or complement each other. For example, Naruto's Rasengan, which is a concentrated form of chakra, might disrupt Majin Android 21's energy flow if they were in combat. On the other hand, Majin Android 21's ability to absorb energy could potentially be used to absorb some of Naruto's chakra attacks, but she might have a hard time dealing with the unique nature of chakra. They could also find ways to combine their powers, like using Naruto's clones to distract an enemy while Majin Android 21 launches a powerful energy blast.
It could be a story where Naruto's positive energy starts to influence Android 21's darker side. Android 21 has a somewhat sinister side to her in the original context. But Naruto's infectious optimism and his belief in the good of people could start to change her. They might go on a journey to find a way to completely purge Android 21 of her negative tendencies, and in the process, they develop a deep bond.
One possible plot could be that Android 21 somehow ends up in the Naruto universe. Maybe she is initially seen as a threat due to her power. Naruto, being the kind - hearted hero, tries to understand her instead of attacking right away. They could team up to fight a common enemy that has the potential to destroy both their worlds.
A possible plot could be that female Android 17 is captured by Orochimaru. Orochimaru wants to study her technology to enhance his own powers. Naruto, upon hearing this, decides to rescue her. Along the way, he has to face Orochimaru's minions and various traps. When he finally reaches Android 17, she is initially distrustful but Naruto convinces her that they need to work together to escape. They then form an unlikely alliance and fight their way out of Orochimaru's lair.
Well, it could start with Naruto on a mission in a strange new land that turns out to be a place where Android 21 exists. They meet and initially misunderstand each other's motives. However, as time passes, Naruto discovers Android 21's softer side. Maybe she has a hidden past that Naruto helps her come to terms with. And in the process, they fall in love. Their relationship could also face opposition from both Naruto's ninja comrades who are suspicious of Android 21, and Android 21's own creators or associates who don't want her involved with Naruto.
The plot might involve the android being an outcast in the shinobi world because she's not human. Naruto, who has always felt like an outsider in some ways, can relate to her. He falls in love as he discovers her hidden emotions and dreams. For example, she might dream of being truly accepted, and Naruto is determined to make that happen. Their love story could be about breaking barriers between different kinds of beings in the Naruto universe.
One interesting majin naruto fanfiction could be about Naruto obtaining majin powers and how it changes his relationships with his friends. For example, Sasuke might view him differently and they'd have new power dynamics.
One interesting idea could be new and unique jutsu combinations. For example, a character might combine a majin - like power with Naruto's Rasengan. Another idea could be different character relationships. Maybe a majin character forms an unexpected alliance with Naruto. And also, there could be new story arcs centered around the mystery of the majin in the Naruto universe.