Another plot idea could be that the collar has a mind of its own. It might sometimes lead Kuroka into unexpected situations. Maybe it has some connection to an ancient power or prophecy. Naruto and Kuroka then have to figure out how to control or use the power of the collar for the greater good of their world.
One idea could be that Kuroka is given a special collar by Naruto that has magical powers. For example, it might enhance her combat abilities or protect her from certain dark magic.
One idea could be a crossover where Naruto's skills in combat and his never - give - up attitude influence the events in the Highschool DxD world. For example, he could help Issei train in a new and unique way, combining ninja techniques with the Boosted Gear. Another plot could involve Kuroka getting involved in a conflict that requires Naruto's special abilities to solve, like a mystery related to ancient ninja scrolls that have somehow ended up in the DxD universe.
It could be Orochimaru. He might be interested in the collar's power and try to steal it from Kuroka. He's always after powerful artifacts and abilities, and this collar could be his next target.
One idea could be a time - travel plot. Imagine Kuroka somehow gets sent to the Naruto universe in the past. Naruto could help her adjust and in the process, they discover a plot by an ancient enemy that they must stop together. This would involve a lot of world - building and exploration of both characters' abilities in a new context.
Perhaps a story where Kuroka transfers to the high school in the Highschool DxD setting and she meets Naruto who is also there for some reason. They could form an unlikely alliance against common enemies. Kuroka's cat - like abilities and Naruto's combat prowess would make for an interesting team - up. And they could also have some comical moments as Naruto tries to understand the strange rules and hierarchies of the Highschool DxD world.
One idea could be exploring Kuroka's past more deeply in the High School DxD universe. Maybe she has some hidden relationships or secrets from her time before joining the main story's events.
One interesting 'naruto collar fanfic' could be about a special collar that has hidden powers. For example, it might be a collar that allows the wearer to access a unique form of chakra. It could be a story where Naruto discovers this collar and has to figure out how to use it while also keeping it a secret from his enemies.
One interesting plot idea could be that Kuroka and Issei have to team up to solve a mystery in the Underworld. Maybe there are strange disappearances of some low - level demons, and they suspect a powerful, hidden force is behind it. As they work together, their relationship deepens from just comrades to something more romantic.
An interesting plot idea for Naruto fanfic might be to focus on the life of a minor character. For instance, what if we told the story of a genin who never made it to be a chunin but still had a significant impact on the village in some other way? Or a story where all the ninja abilities are suddenly switched among the characters, and they have to adapt to these new powers while still facing their usual enemies. This could lead to some really fun and unexpected character interactions.
One idea could be a story where a character is wrongly accused and forced to wear a shock collar as a form of punishment. They then have to prove their innocence while dealing with the pain and limitations the collar imposes. For example, a small-time thief is framed for a big heist and the shock collar is used to keep them from running away while the investigation is ongoing.
The plot might involve Naruto and Kuroka falling in love. They could start off as strangers from different worlds, Naruto from the Hidden Leaf Village and Kuroka from her own realm. As they meet, they gradually find common interests and feelings for each other. Their relationship could face challenges, like disapproval from their respective friends or enemies trying to use their relationship against them. For example, some villains might see their love as a weakness and try to manipulate it to achieve their evil goals. However, through their combined strength and love for each other, they would overcome these difficulties.