- One Piece: Reborn as Enel (Single)
- One Piece: White Hunter (Single)
- One Piece: New Luffy (Harem)
- Paper Paper Fruit In One Piece (Single)
- One Piece: Getting Stronger by Writing a Diary (Harem)
- One Piece: Grand Harem Adventures (Harem)
- Twins of the Sea -Remastered (Completed) (Single)
- One Piece: Lightning's Heir (Single)
- One Piece: Worst Marine (Harem)
- One Piece: Gacha System (Rewriting) (Single)
- Super Saiyan In One Piece World (Harem)
- In One Piece With The Barrier Fruit (Harem) (It's a bad fic, but include a lot of the anime filler material, including the first movies)
- One Piece: Global improvement system (Harem)
- One Piece : Winged Dragons of the Beast Pirates (Single)
- One Piece: The Living Devil (Harem)
- One Piece: Conquering Wanokuni at Start (Harem)
- One Piece: Starting in God Valley as a Slave (Single)
- One Piece: Capitalist Brook's Crew Expansion Plan and One Piece: Hell Pirates (Single) (I'm not sure because the romance is very underdeveloped)
- One Piece: Shadow monarch? I'm Just Logistics! (Single)
- Transmigrated into One Piece world with a Gift Pack (Single)
- One Piece: One Punch Man (Completed) (Harem) (It's a good idea to take a look at the raw, as certain parts seem poorly adapted, especially the grand finale)
A/N: I know these fanfics aren't very faithful to the original story and deviate significantly from the elements and events known today by making use of other things, but unlike other anime, One Piece is a series still in development that's constantly reinventing itself. Just look at the Knights of God and their immortality. These here are the best I could find that meet my requirements.
If you're interested in more fanfics outside of webnovel, let me know.