The idea that master swordsmen use Haki to permanently blacken their blades makes sense. It provides a deeper understanding of how these warriors infuse and seal their Haki into their weapons.

 

Regarding Koby, it's clear he is still far from reaching Luffy's level. While Koby’s ambitions are commendable, he remains significantly outmatched by Luffy in terms of strength, experience, and overall impact. Koby might have a role in the story, but it’s evident that he will remain on a much lower tier compared to Luffy by the end of the series.

 

Luffy, on the other hand, has always been aware of his historical significance, and his Gear 5 form only underscores this. With his recent realization of the historical and cultural importance of his powers, especially in relation to Elbaf, it’s apparent that Luffy will need to navigate these complex contexts. His growing understanding of his role and the profound implications of his abilities further solidifies his central position in the narrative.