Naruto would probably be shocked at first. He might not have expected Hinata to leave him for Kiba. He could be angry at himself for not noticing Hinata's unhappiness sooner.
In such a fanfiction, the plot could involve Hinata feeling unappreciated by Naruto. Maybe Naruto is too focused on his ninja dreams and ignores Hinata's feelings. Kiba, on the other hand, might have been there for Hinata during her low moments, showing her kindness and understanding that Naruto didn't. So, Hinata decides to leave Naruto for Kiba.
In such a fanfiction, they might leave Konoha to start a new life in a peaceful place. Maybe they are tired of the shinobi life full of battles and politics in Konoha. They could find a small village by the sea and build a simple house there, living a quiet life away from the chaos.
Hinata would be heartbroken at first. Naruto is someone she deeply cares about. But she's also a strong - willed ninja. So she might start by trying to understand why Naruto left. She could look for clues in the village or talk to Naruto's friends to figure out his possible destination.
A Hinata leaves Naruto fanfiction could also focus on Hinata leaving to protect Naruto. For example, an enemy might be targeting Naruto and Hinata decides to lead the enemy away from him. This would show her selfless and protective nature. She could then face many challenges on her own while Naruto is left wondering where she went.
In many fanfictions, Hinata might rely on her family for support. For example, her father Hiashi could offer his protection and guidance. She may also find comfort in her friends, like Sakura who could provide medical advice. Additionally, she would likely focus on preparing for the baby's arrival, such as setting up the nursery and gathering necessary supplies.
In some Naruto fanfictions, Hinata could potentially be portrayed as a 'weapon' in a very metaphorical sense. For example, her Byakugan abilities might be exploited in unique ways that make her seem like a strategic weapon for a side or a cause. But in the canon Naruto story, she is a character with her own agency and not really a weapon.
One great source for Naruto and Hinata fanfiction could be FanFiction.net. You can search for stories specifically focused on their relationship there. There are often new and interesting takes on their story, from how they first fell in love to their married life in the future.
Perhaps in the fanfiction, Hinata wears a micro bikini for a special festival in the Hidden Leaf Village. Naruto is really excited to see her in it. They participate in the festival games together and Hinata's new look makes Naruto see her in a different light, more as a strong and confident woman.
One possible plotline could be a story where Naruto has to choose between two versions of Hinata, the original Hinata and a version from an alternate RTN (Road to Ninja) universe. Maybe in this fanfiction, the different Hinatas have unique abilities or personalities that make Naruto's choice more difficult.