Typically, they are often symbols of strength and protection. Their armour can represent their social status, like a noble knight's elaborate armour. They usually have a code of honor associated with their role.
One idea could be Naruto discovers an ancient samurai armour in a hidden cave. The armour has special powers that enhance his ninjutsu. As he puts it on, he feels a connection to the samurai of old and starts to incorporate their fighting styles into his own. He might use the armour to face a new and powerful enemy that is immune to regular ninja attacks.
Maybe the samurai armour is not what it seems. It's actually a disguise for an ancient and powerful demon. Naruto, thinking he's getting an advantage, unknowingly unleashes the demon. Now he has to team up with his enemies to reseal the demon while still wearing the armour that's now part of the demon.
The Karma Seal can change Naruto's appearance. In some fanfictions, it might give him a more menacing look with strange markings spreading across his body.
Well, Armour King has a story filled with determination. He hails from a background where he has trained rigorously in martial arts. In the Tekken tournaments, he faces off against many formidable opponents. His skills are a combination of brute strength and precise technique. He's also known for his loyalty to certain ideals within the fighting community. He has had rivalries that have shaped his journey, making him the respected fighter that he is today.
One possible consequence could be a change in Naruto's power level. If Hinata can control the seal, she might be able to regulate the flow of power from it, which could either enhance or limit Naruto's abilities.
Perhaps an unknown hermit living in some far - off place. In many fanfics, there are mysterious characters that pop up with unique knowledge. This hermit could have mastered the Reaper Death Seal long ago and sees Naruto's potential, so decides to teach him.
One consequence could be that it changes the power dynamics among the Hyuga clan. Since the Caged Bird Seal was used to control the branch family, its removal might lead to a more equal power distribution within the clan.
Neji might gain a significant boost in power. Without the seal suppressing him, his chakra flow could become more natural and stronger. He could potentially unlock new abilities or improve his existing ones, like his Gentle Fist technique becoming even more potent.