In a remote tropical jungle, Yaiba Kurogane, a young boy training in swordsmanship under his father Kenjuurou, has no knowledge of the outside world. One day, father and son end up inside a shipping container headed for Japan, where they encounter Kenjuurou's former rival, Raizou Mine, and his daughter, Sayaka. With few choices, Yaiba accepts a challenge from the Mine family: defeat their strongest student, and he can remain.
Yaiba's extraordinary skill and remarkable strength earn him a place at the dojo. Seeking stronger opponents, he follows Sayaka to school and quickly loses to Takeshi Onimaru, declaring him his new rival. As Onimaru inherits his family's sword and gains demonic powers, Yaiba must push himself to become even stronger in order to ultimately defeat him.