One Piece: Become Stronger by Consuming Devil Fruits

【No female lead, doesn't join the crew, decisive in action, rectifies regrets】

Lin Yuan transmigrates to the world of One Piece, losing all his memories, retaining only the instincts of a Hollow: devouring souls. After a fierce battle with Garp, he's brought back to Windmill Village and entrusted to the mountain bandit Dadan for upbringing.

From then on, Lin Yuan mixes with the three boys, becoming their master and leading them on adventures at sea, allowing them to witness the dark side of pirates and marines firsthand. He unintentionally glimpses their future and forewarns them of their fate, changing their dream of becoming pirates.

Many years later, Luffy smashes his straw hat into Shanks' face: "Shanks, I looked up to you as an idol, but you schemed against me? Run away quickly, don't say..."