Start Punching the Yonko from the Proficiency System

When other people travel through One Piece, they are either overlords or phantom beasts. And I only have one [Proficiency System]. There is no one step to success, only "experience +1" day after day. They laughed at my efforts and ridiculed my mediocrity. Until the war on the top, the sky and the earth are pale, and the strong shed blood. When everyone was in despair, I walked step by step towards the man who was called "the strongest in the world". Whitebeard: "Boy, who are you?" I raised my fists, which were wrapped in jet black color from a million punches, and spoke calmly: "One, an ordinary sailor here to brush up on proficiency."