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.
Maybe in the fanfiction, Goku accidentally uses a new technique that causes him and Android 18 to be mentally linked. Through this link, they start to understand each other on a deeper level. They then find themselves drawn to each other's strength and determination. But they have to hide their growing relationship from their friends and family who might not understand.
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.
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.
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.
The contrast between their worlds. Naruto comes from a world of ninjas, chakra, and elemental powers, while Android 21 is from a more technologically advanced setting with androids and superhuman abilities. When these two are put together in a fanfiction, it creates a unique blend of different concepts that can be really exciting to explore.
One possible plot could be that Krillin discovers a new power within himself while training with Android 18. And as they train, their friendship blossoms into something more. They might have to deal with other Z - fighters being a bit skeptical about their relationship at first. But in the end, they prove that their bond is strong and they are a great team.
Well, it could be a relationship based on power dynamics. Goku is extremely powerful, and Android 21 is no slouch either. They might engage in battles that gradually turn into a form of respect for each other's abilities. And then, this respect could evolve into a deeper connection. For example, Goku could teach Android 21 about the joys of a fair fight, and she could in turn show Goku some of her unique Android - related skills or knowledge.
The plot might involve Naruto trying to prank Android 17 by challenging him to a fake competition. Naruto could pretend to be really bad at it at first, making Android 17 overconfident, and then suddenly show his real skills and win in a very unexpected way, leaving Android 17 shocked.