Haki

Haki is willpower. It is strength that comes from ambitions of some kind. Victory in battle, a desire to be the strongest man, the desires of a king or the will to survive. 

Haki manifests in all kinds of ways. 

Was it outlandish to believe that King could possess the ability to awaken it? The old King wouldn't get the chance to learn about Haki as the power dwells in a different Universe.

However a transmigrated soul who'd studied both Universes with a vigor suddenly finds himself in the body of his favorite character?

That's exactly who Samuel was. An unfortunate lad who ran into the anime worlds in order to escape the strife in his life. 

King was who he saw himself in the most. Someone who had unfortunate circumstances, and escaped with his entertainment. A coward with the heart of a hero.

"One piece holds the best powers for King" Samuel, or "King" now was dwelling in the safety of his room surrounded by the previous vessels games and manga. 

He had bandages over his face, covering his left eye. It was certainly a shock to awaken in a different body and be faced with agonizing pain like that. It did help me figure out exactly who he was and what point in the story he landed in.

Saitama has not yet finished his training, and judging by the lack of gaming equipment lying around, King hasn't been brought into the Hero Association yet. He might still have time to train his Haki.

King's phone began to start ringing, and he wasn't sure whether to pick it up or not.

"May as well bite the bullet." King says to himself. "Hello?" 

"Hello Sir!" This guy sounds like a pen pusher. "This is the Hero Association calling in!" 

Figures.

"I see. What do you guys want from me?" King would not tempt fate like this again. 

"We would like to invite you to join the hero association!" Shit. "Is there any time available for us to meet you in person?" 

Hold on, maybe he can still salvage this. 

"I've got some training to do. How's a month from now?" That should be enough time. 

"That's fine sir! We'll send you the details!" 

Just like that, King's life of heroism began.