Starting With The Sharingan

Hachiro was an avid fan of anime, and his favorite happened to be One Piece. The character he most loved and admired in the show was the all-powerful Whitebeard. Unfortunately, Whitebeard died in the Pirate King battle, which greatly saddened Hachiro.
By some miracle, Hachiro transmigrates to the world of One Piece and gets adopted by Whitebeard as his son. Hachiro lives with the Whitebeard pirates for a year and even makes a name for himself. As it is common for transmigrators to have a cheat skill, Hachiro also has his own. He inherited the ninja skills of Uchiha Itachi from the Naruto anime. Although he was progressing fast, he was still bothered by the future events that would mark the end of Whitebeard. So he decided to go out and train by himself so he could one day have the power to protect his adoptive father.d!"