Perhaps a plot where Toga, who is always fascinated by blood, is intrigued by Naruto's Uzumaki bloodline. She wants to study it but instead of attacking him right away, she decides to follow him secretly. Along the way, Naruto senses her presence but instead of fighting, he offers to talk. This leads to a series of interactions where Toga slowly becomes a reluctant ally of Naruto as they face common enemies together.
Well, a cool plot could be that there's a strange jutsu that accidentally links Naruto and Toga's minds. They start seeing each other's memories and experiences. Naruto sees Toga's difficult past which makes him sympathetic, and Toga gets to understand Naruto's dreams for peace. This connection then leads to them trying to find a way to break the link while also dealing with the changes in their feelings towards each other.
Maybe Villain Deku and Toga team up to take down a common enemy that has wronged them both in the past. As they work together, a strange and dark relationship forms between them. Toga starts to develop deeper feelings for Deku, but he's only focused on revenge at first. However, over time, his view of her might change.
Well, here's a plot. Toga has a vision in which Uraraka is in danger from a new villain. She decides to protect Uraraka, even though they are on opposite sides. Uraraka is initially suspicious but then realizes that Toga is being genuine. This could lead to a strange friendship where they have to keep their relationship a secret from both the heroes and the villains. They could then start to influence each other in small ways, like Uraraka teaching Toga about the value of friendship and Toga showing Uraraka that things aren't always black and white.
One idea could be that in an alternate universe, Bakugou and Toga are forced to team up during a villain - hero cooperation event. They start off hating each other but gradually come to understand each other's motives. Another could be a situation where Toga takes on Bakugou's appearance to get closer to the other heroes and ends up having some really strange interactions with Bakugou himself. Maybe she tries to use his appearance to cause chaos but then realizes she doesn't really want to hurt him in the process.
One idea could be that Toga, in an attempt to understand Izuku better, tries to live a normal life like him for a while. She disguises herself and enrolls in U.A. High, leading to a series of comical and tense situations as she tries to hide her true identity from Izuku and the other students.
One idea could be that they have to overcome the differences in their backgrounds. Izuku is a hero - in - training from a more traditional hero - minded society, while Toga is from a villainous group. Their love could be the catalyst for change in both the hero and villain worlds, as they try to find a way to coexist and be together.
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.