Re: The One Piece 'Ask a Question' Thread
When ace was a prisoner why didn't he use kings haki at all? Is he not skilled enough with it or do seastone cuffs affect haki as well?
Because he didn't had any control over it. As said in the manga the King's Disposition is not something you can actually train like you train your muscles, you can only get a certain amount of control over it, which is not easy and takes years. Ace was still very young. It's not because Luffy got trained for 3 years straight every person would do that. Sengoku pretty much said it during the war that eventually Ace could end up at the top of the Pirate World, but he was talking about the future, indicating that currently Ace wasn't so far yet.
Then you also need to take into account Ace already on death's door when he was in ID due to his fight with BB, which his vivre card that Luffy had showed.
But the most important factor would be Ace's state of mind. Ace had 'doubts'. During the Marineford Arc it was clearly shown that Ace in fact had some kind of an inferiority complex, continuously asking himself whether he should have been born or not and whether he deserved all those people fighting for him. Simply said he didn't value his own existence much, which is in fact quite in contradiction with the nature of the King's Disposition. He had a mental blockade, only in his final moments he truly overcame that mental blockade, but by then it was too late.
Also it's indeed questionable whether seastone handcuffs are affected by Haki or not as IMO that seems a bit too easy, especially in the case of DF users as it zaps their strength.