Modern young man Lin Ye accidentally traveled to the world of One Piece and woke up in a windmill village in the East China Sea. Due to an accidental conflict, he met the young Luffy. The two hit it off because of their common desire to "become a strong man and take risks freely." Luffy excitedly pulled him and shouted, "You should also be my brother, let's be pirates together!" Lin Ye embarked on a journey alongside the future captain of the Straw Hats.
As a time traveler who knows the plot, Lin Ye did not try to change the main line, but chose to protect this adventure in his own way: he reminded Luffy in advance to avoid certain traps, but retained enough challenges for his partners to grow; with his modern understanding of navigation knowledge, he became the "think tank" of the team in the early stages, but never usurped Luffy's dominance.
As he grew up, Lin Ye awakened the unique "Echo Fruit" ability - the ability to briefly copy the afterimages of other people's moves. This allowed him to not only cooperate with Luffy's rubber fruit to perform combos, but also use imitated moves to protect his partners at critical moments. He witnessed Zoro swearing an oath, Nami crying, and Sanji saying goodbye. Each time, he stood beside Luffy as a "brother" and shared risks with his own strength, but always left Luffy with the honor of "becoming the man who became the Pirate King."
The core of the story is not who Lin Ye replaces, but that he re-experiences the passion and bond as an "insider": he will snatch meat with Luffy, will be amused by Usopp's lies, and will collapse with Luffy over Ace's departure during the war.
