One interesting plot in Naruto Armament Haki fanfiction is that the Akatsuki organization somehow gets hold of the knowledge of Armament Haki and starts to train their members in it. This completely changes their power levels and their goals. For example, Pain could use Armament Haki to make his attacks even more devastating. Meanwhile, the Leaf Village has to scramble to understand this new ability and find a way to defend against it. There could also be a plot where a young, unknown ninja has a natural affinity for Armament Haki and is hunted by various factions who want to use his power for their own ends.
One way to incorporate Armament Haki into Naruto fanfiction could be through a crossover concept. Maybe a powerful jutsu creates a rift that brings in elements from the One Piece world where Haki exists. Naruto characters could then start to develop this ability. For example, Naruto, with his strong willpower, might be able to master Armament Haki quickly. It could add a new layer of combat abilities to the existing ninja skills in the Naruto story.
Well, there are 'luffy haki fanfic' stories that focus on the development of his Observation Haki. In some of them, Luffy is able to predict the moves of his opponents far in advance, like being able to dodge attacks that are seemingly impossible to avoid. These fanfics often add new elements to the use of his Haki, like being able to sense the emotions behind an opponent's attack as well.
In this kind of fanfiction, usually the plot might involve Luffy starting to discover his latent conqueror's haki power. Maybe he first experiences some intense battles where he unknowingly shows signs of it. Then, he might meet an old and wise character who recognizes this power in him and starts to guide him on how to control and use it effectively.
You can start by looking on fanfic websites like Archive of Our Own (AO3) or FanFiction.net. Just type 'luffy haki fanfic' into their search bars, and a whole bunch of stories should come up. These platforms have a large collection of One Piece - related fanfics, including those focused on Luffy's Haki.
If Luffy knew Haki early, it would likely give him a significant advantage. He could take on stronger opponents sooner and perhaps even prevent some of the setbacks he faced originally. This could lead to a quicker rise to power and a different dynamic with his crew.
Aside from Luffy, characters like Ace might show up in this type of fanfiction. Ace, being Luffy's brother, could have some connection to Luffy's discovery of conquerer's haki, perhaps through memories or some form of spiritual guidance. Additionally, some powerful enemies might be present. These enemies would serve as the motivation for Luffy to quickly master the conqueror's haki in order to defeat them and protect his crew. There may also be some minor characters from the One Piece world who assist Luffy in his learning process, like the inhabitants of a special village that has knowledge about haki.
In 'naruto haki fanfic', Haki can change the Naruto universe by adding a new layer of power. For example, it can make battles more complex as characters now have to consider both chakra and Haki. It might also change the way characters interact with each other, as those with Haki could sense things differently.
Percy often uses Observation Haki to anticipate the attacks of his enemies. He can sense their movements and intentions, which gives him an edge in combat, especially against fast - moving or sneaky foes like some of the monsters in the Percy Jackson world.