The series follows the titular Yaiba Kurogane a samurai boy inspired by Miyamoto Musashi, the real-life swordsman who made the Hyoho Niten Ichi-ryu style of two-sword fighting and wrote The Book of Five Rings classic on military strategy.

The protagonist, Yaiba (Kurogane Yaiba), is a wild samurai boy who trains in the jungle with his father, Kenjuro. By chance, Yaiba returns to Japan, where he meets his rival Takeshi Onimaru, who has the same samurai spirit as Yaiba, in a new training ground. Yaiba is living a life of serious competition, but when Onimaru obtains the "Legendary Demon Sword", he is on a journey full of spectacle and great adventure.—Crunchyroll News