SI-OC in One Piece's world. The standard pack, adventure, loot, haki and whatnot. Don't want to spoil the MC actions, so I won't tell you anything more. Haki and superpowers will make sense, and I'll try to explain properly the workings of devil fruits in a system that is organic and more or less logical without going against what is explained by Oda, possible Spoilers. Extreme Au.