The dog collar can be a plot device. If it has special powers, it can change the course of battles. For example, if it can create force fields, it can protect the dog and its owner from enemy attacks.
I'm not entirely sure specifically what a 'naruto collar lemon fanfiction' is. 'Naruto' is a popular anime. But 'lemon' in fanfiction often refers to something with romantic or slightly spicy content (not in a vulgar way), and 'collar' might be some sort of unique element within the fan - created story, perhaps related to a particular character's accessory or some sort of power - related concept.
One interesting Naruto collar fanfiction could be about a special collar that has hidden powers and is given to Naruto by a mysterious figure. This collar might enhance his abilities in unique ways.
Probably not. While the Naruto fandom is huge and there are all kinds of fanfictions, 'naruto collar lemon fanfiction' seems like a very particular and perhaps a bit of an odd combination. There are more common themes like Naruto's journey to become Hokage, Sasuke's redemption, or the relationships between the main characters that are more frequently explored in fanfiction. So this type is likely not that common.
Unity is also a theme. The collar can represent the unity between Naruto and Hinata, not just in their relationship but also in their fight against common enemies. It can be a physical manifestation of their shared goals and the strength they get from each other.
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 Naruto white - collar fanfic could be one where Naruto works in a modern corporate setting, using his ninja skills in unexpected ways, like in negotiations. He might use his shadow clone jutsu to be in multiple meetings at once.
I'm not sure specifically which 'Naruto Naruko slave collar' fanfictions are popular. Fanfictions can vary greatly in quality and content. However, you can try searching on fanfiction platforms like FanFiction.net or Archive of Our Own. Maybe look for ones with high ratings and a lot of reviews to find potentially good ones.
First, know the Naruto universe well. Understand the characters, their abilities, and the world they live in. For the collar part, give it a unique backstory. Maybe it was created by an ancient ninja clan. Then, create an interesting plot around it. For example, Naruto could be on a quest to find out the true purpose of the collar.
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.