https://onepiece.fandom.com/wiki/Foxfire_Style
https://onepiece.fandom.com/wiki/Haki/Busoshoku_Haki
Both the ability to cut through fire (Kitsunebi-ryu) and the ability to send one's will to the blade (Ryou) are techniques exclusive to Wano and created by Ryuma.
ワノ国では彼の伝説に追いつかんと、様々な剣術の流派が生まれており、その多くはワノ国の中だけの門外不出の秘技とされている。強な鉄をも両断し、ある剣は龍の吐く炎をも斬り裂くという。
Translation:
In an attempt to catch up with his legend, various schools of swordsmanship have sprung up in Wano, and many of them are considered to be secret techniques exclusive to Wano. It is said that it can cut through strong iron, and some swords can even cut through the flames of a dragon.
