One idea could be that Heather is a new ninja from a far - off land who comes to Konoha. Naruto is immediately intrigued by her unique fighting style. They start training together and gradually develop feelings for each other as they share their ninja dreams and experiences.
Perhaps Heather has a special power that is linked to Naruto's Nine - Tails chakra. When they first meet, there is an unexpected reaction between their powers. This leads them on a journey to understand the connection and in the process, they fall in love. They then have to face challenges from those who fear their combined power.
A possible plot could be that they both enter a local competition, perhaps a writing or a music competition. Charlie Brown is hesitant at first because he's used to not winning. Heather encourages him and they start to practice together. As they work together, they start to understand each other better. Their different personalities - Charlie Brown's pessimism and Heather's optimism - complement each other and they create something truly amazing for the competition.
Well, a plot could revolve around them starting a family. Hiccup and Heather could face difficulties in having children, like dealing with some sort of magical or environmental factor that is affecting their ability to conceive. Or perhaps they adopt a child from a troubled tribe and have to help the child adjust to their new life with them.
One plot idea could be a story where Hiccup, Heather and Lemon are on a quest to find a rare dragon. Along the way, they face various challenges that test their friendship and skills. Hiccup's dragon training knowledge, Heather's combat skills, and Lemon's unique problem - solving abilities all come into play as they battle the elements and other dragon - trainers who want the dragon for themselves.
One idea could be that Naruto and Kashuina meet during a mission outside of Konoha. They start off as rivals, constantly trying to outdo each other in combat skills. But as they face various challenges together, they gradually develop a mutual respect and then deeper feelings. Another plot could be set in a post - war scenario where Naruto, now a hero, meets Kashuina who has a unique ability to heal the psychological scars of the war - torn ninjas. Their interaction then leads to a romantic relationship. And a third idea is that they are both students under a new sensei who pairs them up for special training. During this training, they discover things about each other that they never knew before and fall in love.
One idea could be Naruto being sent to the world of Death Note. He could use his ninja skills to try and outwit Light Yagami. Maybe he would initially be confused by the Death Note's power but then use his determination to stop Light from his killing spree. Another plot could involve Naruto meeting the Shinigami. He might learn about the balance between life and death in this new context and try to find a way to bring some of his ninja world's values to this strange new world.
Perhaps Naruto and Lala meet during a mission where Naruto is sent to a different dimension. Lala, being from an alien world, is intrigued by Naruto's determination and they form an alliance to face a common enemy in that dimension. Their different powers and abilities complement each other, and as they work together, they start to develop feelings for each other.
A more complex plot could be that there is a prophecy in both worlds about a union between someone from the Naruto universe and someone from Ruby's universe. Naruto and Ruby are the ones fated to fulfill this prophecy. They initially don't get along but as they face various challenges together, they start to understand each other and fall in love, while also saving both their worlds in the process.
In a naruto x avatar fanfiction, there could be a scenario where the Akatsuki from Naruto's world teams up with some of the villains from the Avatar world. This would force Naruto and the Avatar (whichever one it may be) to put aside their differences and form an alliance with other characters from both worlds to stop this powerful and evil coalition.
One idea could be that a zombie virus spreads in the Naruto world. Naruto and his friends have to not only fight the zombies but also figure out how the virus started. Maybe Orochimaru was experimenting with dark jutsu and it went wrong.
A possible plot could involve Kefla being sent to the Naruto world as part of a test by the Kais. In this world, she is intrigued by Naruto's determination. Naruto, on the other hand, is amazed by her power. They train together and learn from each other's fighting styles. This leads to a strong bond between them, and they end up protecting the Hidden Leaf Village from a powerful new threat.