Chapter Discussion - Rokushiki is based on Haki, Page 5

Soru, One Piece Role-Play Wiki

One Piece Gold - Rob Lucci's vivre card said that: The training required for the acquisition of rokushiki is akin to that used for acquiring haki. Akin = in the family Rokushiki

Rokushiki, Wiki

Vivre Card Databook – Index Set (some new information) – The Library of Ohara

Rokushiki Robin 32-2 by Shinjojin on DeviantArt

Chapter Discussion - Rokushiki is based on Haki, Page 8

Rokushiki/Tekkai, One Piece Wiki

Rokushiki - Desciclopédia

Chapter Discussion - Rokushiki is based on Haki, Page 7

Why aren't there more characters who uses Rokushiki? Like if you spend your whole life being a swimming champion only to have to eat a Devil Fruit that throws away those years