The sword - Naruto might have the ability to channel his chakra. So it could be used to perform powerful attacks like chakra - infused slashes. Just like how Naruto can use his Rasengan in his normal form, the sword could release a similar type of energy attack when swung with enough force.
It could be due to a magical artifact. Suppose Naruto comes across an ancient and mysterious sword - like artifact. When he touches it or tries to use it, it backfires and instead of him controlling the sword, he is transformed into it. This could lead to a whole new adventure as his friends try to figure out how to reverse the transformation.
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.
Sakura could be a common character. Since she has a history with Naruto, she might be part of the harem in some fanfictions. Also, Tenten could be included as she is another female ninja in the Naruto universe. And Ino, with her strong personality, could also be written into the harem scenario.
One reason could be envy. Maybe Naruto sees Hinata as having something he doesn't, like a more stable family situation, and he lashes out in jealousy. Another reason might be that he's just being a typical, rambunctious kid who doesn't realize the impact of his words or actions on Hinata.
Hinata supports Naruto by being his emotional anchor. When facing the Juubi, Naruto can get caught up in the chaos and danger, but Hinata is there to remind him of his humanity and the things he's fighting for. For example, with a simple look or a kind word, she can calm him down in the heat of battle.
In a fanfiction scenario, Naruto being a jealous husband might lead to some internal conflict. He has always been confident, but when it comes to Hinata's affection, he might worry that he's not doing enough. So, when he sees Hinata having a normal conversation with someone else, he might start to doubt himself. This self - doubt can be explored in the story, and through his relationship with Hinata, he can learn to overcome it.
A Naruto x Hinata fanfiction could focus on a mission they go on together during Naruto Shippuden. They are forced to rely on each other in a dangerous situation. Hinata gets injured protecting Naruto, and Naruto is filled with a new - found determination to protect her. This experience deepens their bond, and Naruto starts to see Hinata in a whole new light, leading to the start of their romantic relationship.